Method for producing long stretched film

ABSTRACT

A method for producing a long stretched film according to one aspect of the present invention includes at least a film forming step of forming a long film made of thermoplastic resin, an oblique stretching step of obliquely stretching the long film and a winding step of winding the long stretched film after the oblique stretching step. The oblique stretching device includes gripping tool travel support tools at opposite sides of the traveling long film. Each of the gripping tool travel support tools includes a plurality of gripping tools. In the oblique stretching device, the gripping tool travel support tools provided at the opposite sides of the long film include the same number of gripping tools. A combination of the gripping tools forming a gripping tool pair is constantly the same at grip start points where the long film is gripped by the gripping tools.

TECHNICAL FIELD

The present invention relates to a method for producing a long stretchedfilm.

BACKGROUND ART

A stretched film formed by stretching resin is used as an optical filmserving various optical functions in various display devices utilizingthe optical anisotropy thereof. For example, in a liquid crystal displaydevice, it is known to use the stretched film as an optical compensationfilm for preventing the coloring of the stretched film for opticalcompensation such as viewing angle expansion and use the stretched filmas a phase difference film doubling as a polarizing plate protectionfilm by bonding the stretched film and a polarizer.

On the other hand, in recent years, attention has been focused onself-luminous display devices such as organic electroluminescencedisplay devices (hereinafter, also referred to as “organic EL displays”)as new display devices. Self-luminance display devices can suppresspower consumption as compared with liquid crystal display devices inwhich a backlight is constantly on. Further, in self-luminous displaydevices in which light sources corresponding to each color arerespectively turned on such as organic EL displays, contrast can befurther enhanced since it is not necessary to dispose color filterswhich cause a contrast reduction. However, since a reflector such as analuminum plate is provided on the back side of the display in theorganic EL display to enhance light extraction efficiency, there is aproblem that outside light incident on the display reduces the contrastof an image by being reflected by this reflector. Thus, it is known touse a circular polarizing plate formed by bonding the stretched film anda polarizer on the front side of the display to improve brightnesscontrast by preventing outside light reflection. Further, such acircular polarizing plate is used also in so-called 3D liquid crystaldisplay devices for displaying a stereoscopic image in some cases.

The above circular polarizing plate needs to be bonded in such anarrangement as to incline an in-plane slow axis of the stretched film ata desired angle with respect to an absorption axis of the polarizer.

However, a general polarizer (polarizing film) is obtained by beingstretched at a high ratio in a conveying direction and the absorptionaxis coincides with the conveying direction. A conventional phasedifference film is produced by being longitudinally or laterallystretched and, in principle, an in-plane slow axis is at 0° or 90° withrespect to a longitudinal direction of the film. Thus, to set an angleof inclination between the absorption axis of the polarizer and the slowaxis of the stretched film at a desired angle as described above, a longpolarizing film and/or stretched film is conveyed and cut at a specificangle and film pieces have to be bonded one by one by a batch method,which has caused problems of deteriorated productivity and a reductionin the yield of products due to the adhesion of chips and the like.Particularly, in these latter days in which organic EL displays arebeing enlarged, if a method for obliquely conveying and cutting anobtained stretched film and bonding the cut piece to a polarizer isused, utilization efficiency of the film is deteriorated andproductivity is deteriorated, wherefore improvement has been necessary.

Contrary to this, various methods for producing a long phase differencefilm have been proposed in which a film is stretched in an obliquedirection at a desired angle and a slow axis can be freely controlled ina direction which is neither at 0° nor at 90° with respect to a widthdirection of the film (see, for example, patent literatures 1 to 4). Inthese methods, while a resin film is delivered in a direction differentfrom a film winding direction after stretching and conveyed withopposite end parts of the resin film gripped by pairs of gripping tools,one and the other gripping tools are moved different distances toobliquely stretch the resin film when a conveying direction is changed,thereby producing a long stretched film having a slow axis at a desiredangle of exceeding 0° and below 90° with respect to a width direction ofthe resin film. By using such a stretched film in which the slow axis isinclined with respect to the width direction, a circular polarizingplate can be produced by bonding a long polarizing film and thestretched film in a roll-to-roll manner instead of conventional bondingby the batch method. Thus, productivity is dramatically improved and ayield can also be drastically improved.

Further, since the circular polarizing plate can be formed by bonding ina roll-to-roll manner, a utilization area of the long stretched film canbe increased and production cost of the circular polarizing plate can bedrastically reduced also in the case of use for large-size displays.

When an image in black display on an organic EL display was viewed inmounting a circular polarizing plate formed using a long stretched filmproduced by an oblique stretching device as described above in theorganic EL display, a phenomenon of so-called “color unevenness” inwhich black was tinged with red or blue and the tinge differs dependingon positions on the display was found.

Further, the above phenomenon was not observed in 3D liquid crystalimage display devices mounted with the circular polarizing plate andfound to be notably observed in organic EL displays mounted with thecircular polarizing plate.

As a result of studying these problems, it was found out that, inself-luminous display devices in which light sources corresponding toeach color are respectively turned on such as organic EL displays unlikeliquid crystal image display devices, there were few members such ascolor filters which caused a contrast reduction and contrast was veryhigh, whereas a slight variation of an optical property was notablyobserved as color unevenness and recognized as a problem.

As a result of further studying such problems, it was found out that thelong stretched film produced by the conventional oblique stretchingdevice described above had a slight variation of an orientation angleover a longitudinal direction of a product and such a slight variationof the orientation angle was observed as color unevenness.

CITATION LIST Patent Literature

-   Patent literature 1: Japanese Patent Application No. 2008-80674-   Patent literature 2: Japanese Patent Application No. 2009-78474-   Patent literature 3: Japanese Patent Application No. 2010-173261-   Patent literature 4: Japanese Patent Application No. 2010-201659

SUMMARY OF INVENTION

The present invention was developed in view of the above conventionalproblems and an object thereof is to provide a method for producing along stretched film which method can suppress a variation of anorientation angle in a width direction in the long stretched filmstretched in an oblique direction and suppress the occurrence of colorunevenness even in the case of use in a circular polarizing plate usedfor an image display device having very high contrast such as an organicEL display.

As a result of scrutinizing the cause of a slight variation of anorientation angle as the cause of color unevenness as described above,it was found out that the slight variation was caused by that a pair ofgripping tools gripping the opposite ends of the long film duringoblique stretching are paired with different gripping tools to startgripping to perform an oblique stretching step at the next grip startpoints after finishing a series of gripping steps from the start to theend of the grip.

In a stretching step, a plurality of gripping tools provided side byside in a conveying direction grip the opposite ends of the long filmand a distance between the paired gripping tools is changed while thegripping tools are moved, whereby the long film is stretched. Suchgripping tools are desirably produced with maximally high accuracy andeach gripping tool has the same properties, but so-called peculiarityoccurs due to a difference in working accuracy, a degree of wear,increase and decrease of lubricant and the like. However, in the case ofconventional lateral stretching, pairs of gripping tools grippingopposite sides of a film are constantly the same combinations and, sincethe film is laterally stretched, no large change is found in theobtained film and an orientation angle is hardly affected even whenthere is a change in the properties of such gripping tools.

On the other hand, in an oblique stretching method in which a deliveringdirection and a winding direction of a long film are different, i.e. astretching method in which traveling distances of the gripping tools aremade different on opposite ends, thereby moving one gripping tool aheadof the other to obliquely stretch a long film as in the presentinvention, combinations of the gripping tool pairs at the grip startpoints inevitably constantly differ in each lap of the gripping toolssince times during which the opposite ends of the long film are grippedare different. Thus, stretching conditions vary when performance changesof the gripping tools as described above occur. Further, it was revealedthat a slight change of the stretching condition caused a variation ofthe orientation angle and color unevenness became apparent in the caseof use as a circular polarizing plate in an organic EL display.Specifically, such a problem either does not occur or is of anunrecognizable level in the case of normal lateral stretching, but hasbecome apparent by producing a long stretched film by oblique stretchingand using such a film in a display device having very high contrast.

Further, it was found that the problem of color unevenness caused bythis variation of the orientation angle in the width direction notablyoccurred in the case of operating the stretching device at a high speedand in the case of thinning the obtained long stretched film.

A method for producing a long stretched film according to one aspect ofthe present invention includes at least a step of forming a long filmmade of thermoplastic resin, an oblique stretching step of deliveringthe long film in a specific direction different from a winding directionof a long stretched film after stretching and obliquely stretching thelong film in a direction of an angle exceeding 0° and below 90° withrespect to a width direction while gripping and conveying opposite endparts of the long film by a plurality of gripping tools of an obliquestretching device and a winding step of winding the long stretched filmafter the oblique stretching step. The oblique stretching deviceincludes gripping tool travel support tools at opposite sides of thetraveling long film. Each of the gripping tool travel support tools atthe opposite sides includes a plurality of gripping tools. The samenumber of the gripping tools are provided at the opposite sides. Acombination of the gripping tools forming a gripping tool pair isconstantly the same at grip start points where the long film is grippedby the gripping tools.

An object, features and advantages of the present invention become moreapparent from the following detailed description along with theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing oblique stretching used in amethod for producing a long stretched film according to one embodimentof the present invention,

FIG. 2 is a schematic diagram of a stretching device according to theembodiment of the present invention,

FIG. 3 is a schematic diagram of a stretching device according to theembodiment of the present invention,

FIG. 4 is a schematic diagram of a stretching device according to theembodiment of the present invention,

FIG. 5 is a schematic diagram of an organic EL display according to theembodiment of the present invention, and

FIG. 6 is a schematic diagram of a stretching device used in ComparativeExamples.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention is described indetail, but the present invention is not limited to this.

As a result of a study to achieve the above object, the presentinventors found out that the above object could be achieved by adjustinggripping tools constituting gripping tool pairs for gripping a long filmfrom opposite sides so that the gripping tools constantly form the samecombinations in an oblique stretching device. The prevent inventorsfurther studied to complete the present invention based on thisknowledge.

Specifically, in the embodiment of the present invention, a method forproducing a long stretched film according to one aspect of the presentinvention includes at least a step of forming a long film made ofthermoplastic resin, an oblique stretching step of delivering the longfilm in a specific direction different from a winding direction of along stretched film after stretching and obliquely stretching the longfilm in a direction of an angle exceeding 0° and below 90° with respectto a width direction while gripping and conveying opposite end parts ofthe long film by a plurality of gripping tools of an oblique stretchingdevice and a winding step of winding the long stretched film after theoblique stretching step. The oblique stretching device includes grippingtool travel support tools at opposite sides of the traveling long film.Each of the gripping tool travel support tools at the opposite sidesincludes a plurality of gripping tools. The same number of the grippingtools are provided at the opposite sides. A combination of the grippingtools forming a gripping tool pair is constantly the same at grip startpoints where the long film is gripped by the gripping tools.

Since the present invention is characterized by the oblique stretchingstep out of the above steps, the oblique stretching step is described inparticular detail.

Here, being long means having a length of at least about five times,preferably a length of ten or more times the width of the film.Specifically, the film can have such a length as to be stored ortransported by being wound into a roll (film roll).

The present invention is specifically described below with reference tothe drawings as appropriate.

<Method for Producing Long Stretched Film>

(Oblique Stretching Step)

The oblique stretching step is a step of stretching a produced long filmin a direction oblique to a width direction. In a method for producing along film, a film of a desired arbitrary length can be formed bycontinuously producing the film. Note that, in the method for producinga long stretched film, the long film may be wound on a winding core toform a rolled body (also referred to as a rolled web) after being formedand, then, may be supplied for the oblique stretching step or the formedfilm may be successively supplied to the oblique stretching step afterthe film forming step without being wound. It is preferable tosuccessively perform the film forming step and the oblique stretchingstep since film formation conditions can be changed by feeding back theresults of a film thickness and optical values after stretching and adesired long stretched film can be obtained.

In the long stretched film producing method of this embodiment, the longstretched film is produced which has a slow axis at an angle exceeding0° and below 90° with respect to a width direction of the film. Here,the angle with respect to the width direction of the film is an angle inthe plane of the film. Since the slow axis in the plane of the filmnormally appears in a stretching direction or a direction perpendicularto the stretching direction, the long stretched film having such a slowangle can be produced by performing stretching at the angle exceeding 0°and below 90° with respect to an extending direction of the film.

An angle between the width direction of the long stretched film and theslow axis, i.e. an orientation angle can be arbitrarily set at a desiredangle in a range exceeding 0° and below 90°.

(Stretching by Oblique Stretching Device)

To orient the long film to be stretched in this embodiment in an obliquedirection, the oblique stretching device is used. The oblique stretchingdevice used in this embodiment is preferably a film stretching devicecapable of freely setting the orientation angle of the film, orientingan orientation axis of the film laterally uniformly in the film widthdirection with high accuracy and controlling a film thickness andretardation with high accuracy by variously changing route patterns ofgripping tool travel support tools.

FIG. 1 is a diagram showing oblique stretching used in the longstretched film producing method of this embodiment. This is only anexample and the present invention is not limited to this.

A delivering direction D1 of the long film is different from a windingdirection D2 of the long stretched film after stretching, therebyforming a delivery angle θi. The delivery angle θi can be arbitrarilyset at a desired angle in the range exceeding 0° and below 90°.

Opposite ends of the long film are gripped by left and right grippingtools (gripping tool pair) at the entrance of the oblique stretchingdevice (grip start points where the gripping tools grip the long film, astraight line connecting the grip start points is denoted by A) and thelong film travels as the gripping tools travel.

The gripping tool pair is composed of the left and right gripping toolsCi, Co facing in a direction substantially perpendicular to a travelingdirection (delivering direction D1) of the long film at the entrance ofthe oblique stretching device. The left and right gripping tools Ci, Corespectively travel along bilaterally asymmetric routes and the grippedlong stretched film is released at a position where stretching isfinished (grip release points where the gripping tools release the grip,a straight line connecting the grip release points is denoted by B).

At this time, as the left and right gripping tools facing each other atthe entrance (position A in FIG. 1) of the oblique stretching devicerespectively travel along an inner gripping tool travel support tool Riand an outer gripping tool travel support tool Ro, which are bilaterallyasymmetric, the gripping tool Ci traveling along the inner gripping tooltravel support tool Ri is in a positional relationship to be ahead ofthe gripping tool Co traveling along the outer gripping tool travelsupport tool Ro.

Specifically, in a state where the gripping tools Ci, Co facing eachother in the direction substantially perpendicular to the deliveringdirection D1 of the long film at the entrance of the oblique stretchingdevice are at positions B, the straight line connecting the grippingtools Ci, Co is inclined by an angle θL with respect to the directionsubstantially perpendicular to the winding direction D2 of the longstretched film.

By the above operation, the long film is obliquely stretched in adirection of θL. Here, substantially perpendicular means within a rangeof 90±1°.

The producing method of the present invention is carried out using astretching device capable of oblique stretching. This stretching deviceis a device for heating the long film at an arbitrary temperature atwhich the long film can be stretched and obliquely stretching the longfilm. This stretching device includes a heating zone, a plurality ofgripping tools which travel while gripping the opposite sides of thelong film and are paired on the both sides, and gripping tool travelsupport tools for supporting the travel of the gripping tools.

The opposite ends of the long film successively supplied to an entrancepart (grip start points) of the stretching device are gripped by thegripping tools, and the long film is introduced into the heating zoneand released from the gripping tools at an exit part (grip releasepoints) of the stretching device. The long stretched film released fromthe gripping tools is wound on a winding core. The gripping tool travelsupport tools each including the gripping tools have an endlesscontinuous path and the gripping tools having released the longstretched film at the exit part of the stretching device aresuccessively returned to the grip start points by the gripping tooltravel support tools.

The gripping tool travel support tool may be, for example, such that anendless chain whose path is restricted by a guide rail or a gearincludes gripping tools or such that an endless guide rail includesgripping tools. Specifically, in the present invention, the grippingtool travel support tool may be an open-ended guide rail including anendless chain, an endless guide rail including an endless chain or anendless guide rail including no chain. The gripping tools travel along aroute of the gripping tool travel support tool if the gripping tooltravel support tool includes no chain while traveling along the route ofthe gripping tool travel support tool via a chain if the chain isincluded. Although a case where the gripping tools travel along theroute of the gripping tool travel support tool is described as anexample in the present invention, the gripping tools may travel alongthe route of gripping tool travel support tool via the chain providedwith the gripping tools in either case.

Note that the gripping tool travel support tools of the stretchingdevice are shaped to be bilaterally asymmetric and route patterns can bemanually or automatically adjusted according to the orientation angle tobe given to the long stretched film to be produced, a stretch ratio andthe like.

In the stretching device of this embodiment, preferably, the route ofeach gripping tool travel support tool can be freely set and the patternof the route of the gripping tool travel support tool can be arbitrarilychanged.

In the embodiment of the present invention, a traveling speed of thegripping tool of the stretching device can be appropriately selected.Above all, 1 to 150 m/min is preferable. If the traveling speed of thegripping tool of the stretching device is faster than 150 m/min, a localstress applied to an end part of the film increases at a position wherethe long film is obliquely conveyed, whereby the end part of the film iswrinkled or shifted and an effective width obtained as a good productout of the entire width of the film obtained after the end of stretchingtends to be narrow.

In the present invention, a difference in the traveling speed of thegripping tool pairs at least gripping the film is normally 1% or less,preferably 0.5% or less and more preferably 0.1% or less of thetraveling speed. The traveling speeds are substantially equal. This isbecause a speed difference of the left and right gripping toolsconstituting the gripping tool pairs is required to be substantiallyzero since the film is wrinkled or shifted at the end of the stretchingstep if there is a difference in the traveling speed of the longstretched film on the left and right sides at the end of the stretchingstep. In a general stretching device or the like, speed unevennessoccurs in the order of seconds or less according to the pitch of teethof a sprocket (gear) for driving a chain, a frequency of a drive motorand the like. This speed unevenness is often several %, but these do notfall under the speed difference described in this embodiment.

The lengths (entire lengths) of the gripping tool travel support toolsare not particularly limited. As shown in FIG. 2, if the gripping tooltravel support tools have the same length, the same number of grippingtools traveling at an equal speed can constantly form the gripping toolpairs by being paired with the same gripping tools paired at first. As aresult, a variation of the orientation angle can be suppressed bysetting proper combinations according to properties of the gripping toolpairs. Even if a property changes in some gripping tools, such a changecan be easily detected, the gripping tools can be properly adjusted tosuppress a variation of the orientation angle and, as a result, theoccurrence of color unevenness can be suppressed. FIG. 2 is a schematicdiagram of a stretching device T1 in which the route of the innergripping tool travel support tool Ri and that of the outer gripping tooltravel support tool Ro have the same length.

The step of stretching the long stretched film in the present inventionis described more specifically with reference to FIG. 2. As shown inFIG. 2, the gripping tools (gripping tools 1 i, 1 c) are adjusted togrip widthwise end parts of the long film at the grip start points onthe straight line A. The gripping tool 1 i that travels along the routeof the inner gripping tool travel support tool Ri and the gripping tool1 o that travels along the route of the outer gripping tool travelsupport tool Ro are aligned on the straight line A.

Each of the gripping tools of the gripping tool travel support tools onthe both sides has an endless continuous path and travels along thegripping tool travel support tool. The gripping tools grip the long filmsupplied at the grip start points and release the long stretched film Fat the grip release points on the straight line B after stretching. Eachgripping tool having released the long stretched film F continues totravel along the gripping tool travel support tool, reaches the gripstart point again and grips the long film continuously supplied. In thisway, the gripping tools circle along the gripping tool travel supporttools and repeatedly grip, stretch and release the supplied long film.These movements are successively performed by the gripping tool pairformed by one gripping tool traveling along the route of the innergripping tool travel support tool Ri and one gripping tool travelingalong the route of the outer gripping tool travel support tool Ro. Inthe present invention, the combination of the gripping tools forming thegripping tool pair is constantly the same.

Note that a separating distance between the gripping tools forming thegripping tool pair is equivalent to the width of the supplied long film.The long film is conveyed together with the traveling gripping tools andpasses through unillustrated preheating zone, stretching zone, thermalfixing zone and cooling zone. The gripping tool traveling along theroute of the inner gripping tool travel support tool Ri reaches the griprelease point and releases the long stretched film earlier than thegripping tool traveling along the route of the outer gripping tooltravel support tool Ro. Note that when the gripping tool traveling alongthe route of the inner gripping tool travel support tool Ri reaches thegrip release point, the other gripping tool paired with the formergripping tool at the grip start point has not reached the grip releasepoint yet and is traveling along the route of the outer gripping tooltravel support tool Ro.

In FIG. 2, the straight line B connecting the grip release points of thegripping tools 1 i traveling along the route of the inner gripping tooltravel support tool Ri and that of the gripping tools to traveling alongthe route of the outer gripping tool travel support tool Ro is notparallel to the width direction of the traveling long stretched film F.Further, the length of the route of the inner gripping tool travelsupport tool Ri and that of the route of the outer gripping tool travelsupport tool Ro are equal. As shown in FIG. 2, a turning gear G1provided near the grip release point of the inner gripping tool travelsupport tool is arranged downstream of a turning gear G2 provided nearthe grip release point of the outer gripping tool travel support tool inthe traveling direction of the long stretched film F. As a result, anangle θ between the straight line B and the traveling direction of thelong stretched film F is larger than 0° and below 90°. In this case, astress applied to the long stretched film F by the gripping tool 1 itraveling along the route of the inner gripping tool travel support toolRi when the long stretched film F is released and a stress applied tothe long stretched film F by the gripping tool 1 o traveling along theroute of the outer gripping tool travel support tool R0 when the longstretched film F is released do not cancel out each other. As a result,there is a possibility of thickness unevenness in the obtained longstretched film F. Thus, the straight line B connecting the grip releasepoints is preferably parallel to the width direction of the longstretched film F. Note that, in the stretching device T1 of FIG. 2, anadjusting gear G3 is provided in the inner gripping tool travel supporttool Ri to make the length of the route of the inner gripping tooltravel support tool Ri equal to that of the route of the outer grippingtool travel support tool Ro. The adjusting gear G3 is a gear forstretching the inner gripping tool travel support tool Ri toward anouter side in a circumferential direction.

FIG. 3 is a schematic diagram of a stretching device T2 formed such thatthe length of a route of an inner gripping tool travel support tool Riand that of a route of an outer gripping tool travel support tool Ro areequal and a straight line connecting grip release points is parallel toa width direction of a long stretched film F. As shown in FIG. 3, anangle θa between the straight line connecting the grip release pointsand a traveling direction of the long stretched film F is 90°. A turninggear G1a provided near the grip release point of the inner gripping tooltravel support tool is arranged upstream of the turning gear G1 of FIG.2 in a traveling direction of the long stretched film F. As a result,the straight line B is parallel to the width direction of the longstretched film F. In this case, there is a possibility of deflecting theinner gripping tool travel support tool. Thus, as shown in FIG. 3, anadjusting gear G3a is provided in the inner gripping tool travel supporttool. The adjusting gear G3a is a gear for stretching the inner grippingtool travel support tool toward an outer side in a circumferentialdirection to eliminate the deflection of the inner gripping tool travelsupport tool caused by changing the position of the turning gear G1.

By producing the long stretched film F using the stretching device T2,stresses applied to the long stretched film F are canceled out atopposite widthwise end parts of the long stretched film particularlywhen the gripping tools release the long stretched film F at the griprelease points. Thus, thickness unevenness of the obtained longstretched film F is reduced.

On the other hand, if it is difficult to make the entire lengths of thegripping tool travel support tools equal in the configuration of thestretching device, a speed adjusting mechanism (not shown) forincreasing and decreasing the traveling speeds of the gripping tools maybe provided in one or both of the gripping tool travel support tools asin a stretching device T3 shown in FIG. 4. In FIG. 4, a case isillustrated where the speed adjusting mechanism for increasing thetraveling speed of gripping tools traveling along a route of an outergripping tool travel support tool Ro is provided. The speed adjustingmechanism is a mechanism for adjusting the traveling speed of thegripping tool 1 o having released the long film F at the grip releasepoint until the gripping tool 1 o returns to the grip start point again.A method for adjusting the traveling speed of the gripping tool is notparticularly limited. For example, the traveling speed of the grippingtool may be increased or decreased such as by inclining the grippingtool travel support tool, by blowing air, by generating a magnetic fieldor by dividing the gripping tool travel support tool into a plurality ofsections having different friction coefficients. The traveling speeds ofthe gripping tools can be adjusted by decreasing the speed of thegripping tools traveling along the route of the gripping tool travelsupport tool having a shorter entire length, increasing the speed of thegripping tools traveling along the route of the gripping tool travelsupport tool having a longer entire length or by combining the bothadjustments. In FIG. 4, C denotes a section in which the traveling speedof the gripping tool is adjusted by the speed adjusting mechanism. Inthis embodiment, this section is a section in which the gripping toolhaving released the grip at the grip release point travels and a sectionuntil the grip start point is reached. As shown in FIG. 4, the grippingtools to accelerated by the speed adjusting mechanism travel in thesection C. By adjusting the traveling speeds of the gripping tools inthis way, the entire lengths of the routes of the gripping tool travelsupport tools need not be made equal and a drastic design change of thedevice is not necessary. Further, it is possible to calculate how muchthe speed of the gripping tool needs to be adjusted in advance when thepatterns of the routes of the gripping tool travel support tools and astretching angle are adjusted. As a result, in the producing method ofthe present invention, the traveling speeds of the gripping tools can beso immediately adjusted that the same gripping tool pairs are constantlyaligned at the grip start points in the case of changing the stretchingangle or the like, which provides good convenience. Note that although acase where an angle θb between a straight line connecting the griprelease points and the traveling direction of the long stretched film Fis 90° is shown in FIG. 4, the angle θb may be larger than 0° and below90° as in the stretching direction T1 shown in FIG. 2.

In the oblique stretching device used in this embodiment, the grippingtool travel support tools for restricting the path of the gripping toolsare often required to have a large bending rate particularly atpositions where the conveying direction of the long film is inclined.For the purpose of avoiding the interference of the gripping tools or alocal stress concentration caused by steep bending, the paths for thegripping tools are desirably arcuate at bent parts.

In this embodiment, the long film travels as the gripping tools travelwhile the opposite ends thereof are successively gripped by the left andright gripping tools (gripping tool pair) at the entrance of the obliquestretching device (position of the straight line A of FIG. 1). At theentrance of the oblique stretching device, the pair of gripping toolsfacing each other in the direction substantially perpendicular to thelong film traveling direction D1 travel along the bilaterally asymmetricroutes and pass through a heating zone including the preheating zone,the stretching zone and the thermal fixing zone.

The preheating zone indicates a section in which the gripping toolsgripping the opposite ends travel while keeping a constant spacingtherebetween at an entrance part of the heating zone.

The stretching zone indicates a section in which the spacing between thegripping tools gripping the opposite ends starts increasing and reachesa predetermined spacing. Although the long film can be stretched in anoblique direction in the stretching zone in the present invention, itmay be obliquely stretched after being laterally stretched in thestretching zone or may be stretched in the width direction after beingobliquely stretched without being limited to stretching in the obliquedirection.

The thermal fixing zone indicates a section in which the gripping toolson the opposite ends travel while being kept in parallel with each otherfor a period during which the spacing between the gripping tools isconstant again after the stretching zone. After passing through thethermal fixing zone, the long film may pass through a section in whichtemperature is set at a glass transition temperature Tg° C. ofthermoplastic resin constituting the long film or lower (cooling zone).At this time, such route patterns as to narrow the spacing between thegripping tools facing each other in advance may be adopted inconsideration of the shrinkage of the long stretched film caused bycooling.

In the present invention, lateral stretching and longitudinal stretchingmay be performed if necessary in a step before or after the long film isintroduced into the oblique stretching device for the purpose ofadjusting mechanical properties and optical properties of the film.

Temperature in each zone is preferably set based on the glass transitiontemperature Tg of the thermoplastic resin as follows. The temperature ofthe preheating zone is Tg to Tg+30° C. The temperature of the stretchingzone is Tg to Tg+30° C. The temperature of the cooling zone is Tg−30° C.to Tg.

Note that a temperature difference may be provided in the widthdirection in the stretching zone to control thickness unevenness in thewidth direction. To provide a temperature difference in the widthdirection in the stretching zone, it is possible to use a known methodsuch as a method for adjustment to make an opening of a nozzle forblowing hot air into a thermostatic chamber different in the widthdirection or a method for heating control by arranging heaters in thewidth direction. The lengths of the preheating zone, the stretching zoneand the thermal fixing zone can be appropriately selected. The length ofthe preheating zone is normally 100 to 150% of the length of thestretching zone, and that of the thermal fixing zone is normally 50 to100% of the length of the stretching zone. Further, the cooling zone maybe provided after the thermal fixing zone.

A stretch ratio R (W/W0) in the stretching step is preferably 1.3 to 3.0and more preferably 1.5 to 2.8. It is preferable that the stretch ratiois in this range since thickness unevenness in the width direction isreduced. In the stretching zone, thickness unevenness in the widthdirection can be further improved to a better level if stretchingtemperature is varied in the width direction. Note that W0 denotes thewidth of the long film before stretching and W denotes the width of thelong stretched film after stretching.

Next, other steps that can be adopted in the present invention aredescribed. Note that it is sufficient to provide the oblique stretchingstep described above and other steps are not particularly limited. Thus,the other steps described below are illustrative and design changes canbe made as appropriate.

(Film Forming Step of Long Film)

The film forming step is a step of forming the long film made ofthermoplastic resin.

The long film to be formed in this embodiment is not particularlylimited and may be any long film made of thermoplastic resin.

For example, in the case of using the long stretched film afterstretching for optical application, a film made of resin having aproperty of being transparent at a desired wavelength is preferable.Examples of such resin may include polycarbonate-based resin, polyethersulfone-based resin, polyethylene terephthalate-based resin,polyimide-based resin, polymethyl methacrylate-based resin,polysulfone-based resin, polyarylate-based resin, polyethylene-basedresin, polyvinyl chloride-based resin, olefin polymer-based resin havingan alicyclic structure and cellulose ester-based resin. Among these,polycarbonate-based resin, olefin polymer-based resin having analicyclic structure and cellulose ester-based resin are preferable interms of transparency and mechanism strength. Among them, olefinpolymer-based resin having an alicyclic structure and celluloseester-based resin that facilitate an adjustment of a phase difference inthe case of use as an optical film are further preferable. Among them,olefin polymer-based resin having an alicyclic structure is particularlypreferable since end parts of the film are unlikely to be wrinkled orshifted due to a low stretching stress even when the film is obliquelystretched during high-speed conveyance.

<Alicyclic Olefin Polymer-Based Resin>

A cyclic olefin random multi-component copolymer disclosed in JapaneseUnexamined Patent Publication No. H05-310845, a hydrogen-added polymerdisclosed in Japanese Unexamined Patent Publication No. H05-97978, athermoplastic dicyclopentadiene-based ring-opening polymer and ahydrogenated product thereof disclosed in Japanese Unexamined PatentPublication No. H11-124429 can be used as alicyclic olefin polymer basedresin.

The olefin polymer-based resin having an alicyclic structure is morespecifically described. The olefin polymer-based resin having analicyclic structure is a polymer having an alicyclic structure such as asaturated alicyclic hydrocarbon (cycloalkane) structure or anunsaturated alicyclic hydrocarbon (cycloalkene) structure. There is noparticular limit to the number of carbon atoms constituting an alicyclicstructure, but when the number of carbon atoms is normally in a range of4 to 30, preferably in a range of 5 to 20 and more preferably in a rangeof 5 to 15, mechanical strength, heat resistance and moldability of thelong film are highly balanced, which is preferable.

A ratio of repeating units including an alicyclic structure in analicyclic olefin polymer may be appropriately selected, but preferably55 weight % or more, further preferably 70 weight % or more andparticularly preferably 90 weight % or more. It is preferable that theratio of the repeating units including the alicyclic structure in thealicyclic olefin polymer is in this range since transparency and heatresistance of an optical material such as a phase difference filmobtained from the long stretched film of the present invention areimproved.

Examples of olefin polymer-based resins having an alicyclic structuremay include norbornene-based resin, single cyclic olefin-based resin,cyclic conjugated diene-based resin, vinyl cyclic hydrocarbon-basedresin and hydrogenated products of these. Among these, norbornene-basedresin can be suitably used since transparency and moldability are good.

Examples of norbornene-based resin may include ring-opening polymers ofmonomers having a norbornene structure, ring-opening copolymers ofmonomers having a norbornene structure and other monomers, hydrogenatedproducts thereof, addition polymers of monomers having a norbornenestructure, and addition copolymers of monomers having a norbornenestructure and other monomers and hydrogenated products thereof. Amongthese, hydrogenated products of ring-opening (co)polymers of monomershaving a norbornene structure can be particularly suitably used in termsof transparency, moldability, heat resistance, low hygroscopicity,dimensional stability and light weight.

Examples of monomers having a norbornene structure may includebicyclo[2.2.1]hept-2-ene (trivial name: norbornene),tricyclo[4.3.0.12,5]deca-3,7-dien (trivial name: dicyclopentadiene),8-benzotricyclo[4.3.0.12,5]deca-3-ene (trivial name:methanotetrahydrofluorene), tetracyclo[4.4.0.12,5.17,10]dodeca-3-ene(trivial name: tetracyclododecene) and derivatives of compounds of these(e.g. those including a substituent in a ring). Here, examples of thesubstituent may include an alkyl group, an alkylene group and a polargroup. A plurality of the same or different ones of these substituentsmay be bonded to a ring. Monomers having a norbornene structure can besingly used or two or more kinds thereof may be used in combination.

Kinds of the polar group may include a heteroatom and an atom groupincluding a heteroatom. Examples of the heteroatom may include an oxygenatom, a nitrogen atom, a sulfur atom, a silicon atom and a halogen atom.Specific examples of the polar group may include a carboxyl group, acarbonyloxycarbonyl group, an epoxy group, a hydroxy group, an oxygroup, an ester group, a silanol group, a silyl group, an amino group, anitrile group and a sulfo group.

Examples of other monomers capable of ring-opening copolymerization withmonomers having a norbornene structure may include monocyclic olefinssuch as cyclohexane, cycloheptene and cyclooctene and derivativesthereof; and cyclic conjugated dienes such as cyclohexadiene andcycloheptadiene and derivatives thereof.

Ring-opening polymers of monomers having a norbornene structure andring-opening copolymers of monomers having a norbornene structure andother monomers capable of copolymerization with the former monomers canbe obtained by (co)polymerizing monomers under the presence of a knownring-opening polymerization catalyst.

Examples of other monomers capable of addition copolymerization withmonomers having a norbornene structure may include α-olefins having acarbon number of 2 to 20 such as ethylene, propylene and 1-butene andderivatives thereof; cycloolefines such as cyclobutene, cyclopentene andcyclohexane and derivatives thereof; and non-conjugated dienes such as1,4-hexadiene, 4-methyl-1,4-hexadiene and 5-methyl-1,4-hexadiene. Thesemonomers can be singly used or two or more kinds thereof may be used incombination. Among these, α-olefins are preferable and ethylene is morepreferable.

Addition polymers of monomers having a norbornene structure and additioncopolymers of monomers having a norbornene structure and other monomerscapable of copolymerization with the former monomers can be obtained bypolymerizing monomers under the presence of a known additionpolymerization catalyst.

Hydrogenated products of ring-opening polymers of monomers having anorbornene structure, hydrogenated products of ring-opening copolymersof monomers having a norbornene structure and other monomers capable ofring-opening copolymerization with the former monomers, hydrogenatedproducts of addition polymers of monomers having a norbornene structureand hydrogenated products of addition copolymers of monomers having anorbornene structure and other monomers capable of copolymerization withthe former monomers can be obtained by adding a known hydrogenationcatalyst containing a transition metal such as nickel or palladium tosolutions of these polymers and hydrogenating preferably 90% or more ofcarbon-carbon unsaturated bonds.

Among norbornene-based resins, preferable ones are such that X:bicyclo[3.3.0]octane-2,4-diyl-ethylene structure and Y:tricyclo[4.3.0.12,5]decane-7,9-diyl-ethylene structure are included asrepeating units, the content of these repeating units is 90 weight % ormore of all the repeating units of the norbornene-based resin, and thecontent of X and the content of Y are 100:0 to 40:60 in a weight ratioof X:Y. By using such resin, an optical material obtained from the longstretched film of the present invention has no dimensional change in thelong term and can be excellent in optical property stability.

A molecular weight used for norbornene-based resin is appropriatelyselected according to intended use, but is normally 10,000 to 100,000,preferably 15,000 to 80,000 and more preferably 20,000 to 50,000 inweight average molecular weight (Mw) in terms of polyisoprene (in termsof polystyrene if a solvent is toluene) measured by gel permeationchromatography using cyclohexane as a solvent (toluene if thermoplasticresin is not dissolved). It is preferable that the weight averagemolecular weight is in such a range since mechanical strength andmoldability of the optical material obtained from the long stretchedfilm of the present invention are highly balanced.

A glass transition temperature of the norbornene-based resin may beappropriately selected according to intended use, but preferably 80° C.or higher and more preferably in a range of 100 to 250° C. If the glasstransition temperature is in such a range, the optical material obtainedfrom the long stretched film of the present invention can be excellentin durability without being deformed or stressed in use under a hightemperature.

A molecular weight distribution (weight average molecular weight(Mw)/number average molecular weight (Mn)) of the norbornene-based resinis not particularly limited, but normally in a range of 1.0 to 10.0,preferably in a range of 1.1 to 4.0 and more preferably in a range of1.2 to 3.5.

An absolute value of a photoelastic coefficient C of thenorbornene-based resin is preferably 10×10⁻¹² Pa⁻¹ or smaller, morepreferably 7×10⁻¹² Pa⁻¹ or smaller and particularly preferably 4×10⁻¹²Pa⁻¹ or smaller. The photoelastic coefficient C is a value expressed byΔn/σ if Δn denotes birefringence and σ denotes stress. If thephotoelastic coefficient of the thermoplastic resin is in such a range,a variation of retardation (Re) in an in-plane direction can be reduced.

The thermoplastic resin used in the present invention may beappropriately mixed with a colorant such as a pigment and a dye or acompounding agent such as a fluorescent brightening agent, a dispersant,a heat stabilizer, a light stabilizer, an ultraviolet absorbing agent,an antistatic, an antioxidant, a lubricant and a solvent.

The content of remaining volatile components in the long stretched filmof the norbornene-based resin is not particularly limited, butpreferably 0.1 mass weight % or less, more preferably 0.05 mass weight %or less and further preferably 0.02 mass weight % or less. By settingthe content of the volatile components in such a range, dimensionalstability is improved and changes of Re and Rth described above withtime can be reduced. Further, the deterioration of a phase differencefilm, a polarizing plate or an image display device such as an organicEL display obtained from the long stretched film of the presentinvention can be suppressed and the display of the image display devicesuch as an organic EL display can be stably and satisfactorilymaintained in the long term. The remaining volatile components are atiny amount of substances having a molecular weight of 200 or less andcontained in the long film and examples thereof may include remainingmonomers and solvent. The content of the remaining volatile componentscan be quantified by analyzing the long film by gas chromatography as atotal of substances contained in the long film and having a molecularweight of 200 or less.

A saturated water absorption of the long stretched film of thenorbornene-based resin is preferably 0.03 mass % or less, furtherpreferably 0.02 mass % or less and particularly preferably 0.01 mass %or less. If the saturated water absorption is in the above range,changes of Re and Rth with time can be reduced. Further, thedeterioration of a phase difference film, a polarizing plate or an imagedisplay device such as an organic EL display obtained from the longstretched film of the present invention can be suppressed and thedisplay of the image display device such as an organic EL display can bestably and satisfactorily maintained in the long term.

The saturated water absorption is a value expressed as a percentage ofan increased mass to a test piece mass before immersion when the testpiece of the long film is immersed in water of a given temperature for agiven time. Normally, a measurement is made after the test piece isimmersed in water of 23° C. for 24 hours. The saturated water absorptionof the long stretched film of the present invention can be adjusted tothe above value, for example, by reducing the amount of polar groups inthe thermoplastic resin, but the thermoplastic resin is desirably resinhaving no polar group.

Producing methods such as solution film formation methods and meltextrusion methods are preferred as a method for forming the long filmusing the above preferable norbornene-based resin. An inflation methodusing a die and the like can be cited as the melt extrusion method, buta method using a T-die is preferable in terms of excellent productivityand thickness precision.

An extrusion molding method using a T-die can produce a long film withgood variations of optical properties such as retardation and anorientation angle by a method for keeping molten thermoplastic resin ina stable state when the thermoplastic resin is brought into closecontact with a cooling drum as disclosed in Japanese Unexamined PatentPublication No. 2004-233604.

Specific examples of the method may include 1) a method for bringingsheet-like thermoplastic resin extruded from a die into close contactwith a cooling drum to take up the sheet-like thermoplastic resin undera pressure of 50 kPa or lower in producing a long film by the meltextrusion method; 2) a method for covering an area from an opening of adie to a cooling drum with which a long film is to be first brought intoclose contact by a covering member and setting a distance from thecovering member to the opening of the die or the cooling drum with whichthe long film is to be first brought into close contact to 100 mm orshorter in producing the long film by the melt extrusion method; 3) amethod for heating an atmosphere within 10 mm from sheet-likethermoplastic resin extruded from an opening of the die to a specifictemperature in producing a long film by the melt extrusion method; 4) amethod for bringing sheet-like thermoplastic resin extruded from a dieto satisfy a relationship into close contact with a cooling drum to takeup the sheet-like thermoplastic resin under a pressure of 50 kPa orlower; and 5) a method for blowing air at a speed different from atake-up speed of a cooling drum with which a long film is to be firstbrought into close contact by 0.2 m/s or less to sheet-likethermoplastic resin extruded from an opening of a die in producing thelong film by the melt extrusion method.

This long film may be a single-layer film or a laminated film composedof two or more layers. The laminated film can be obtained by knownmethods such as a co-extrusion molding method, a co-casting moldingmethod, a film lamination method and a coating method. Among these, theco-extrusion molding method and the co-casting molding method arepreferable.

<Cellulose Ester-Based Resins>

Resin containing cellulose acylate satisfying the following expressions(i) and (ii) and a compound expressed by the following generalexpression (A) can be cited as cellulose ester-based resin.

2.0≦Z1≦3.0  Expression (i)

0.5≦X  Expression (ii)

(In the expressions (i) and (ii), Z1 denotes a total degree of acylsubstitution of cellulose acylate and X denotes the sum of a degree ofpropionyl substitution and a degree of butyryl substitution of celluloseacylate.)

(Compound of Generation Expression (A))

The generation expression (A) is described in detail below.

In the generation expression (A), L₁, L₂ independently denote monovalentor bivalent linking groups.

The following structure can be, for example, cited as L₁, L₂ (R belowdenotes a hydrogen atom or substituent).

L₁, L₂ are preferably —O—, —COO— or —OCO—. R₁, R₂ and R₃ independentlydenote substituents.

Specific examples of the substituents expressed by R₁, R₂ and R₃ mayinclude halogen atoms (fluorine atom, chloride atom, bromine atom,iodine atom, etc.), alkyl groups (methyl group, ethyl group, n-propylgroup, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexylgroup, etc.), cycloalkyl groups (cyclohexyl group, cyclopentyl group,4-n-dodecyl cyclohexyl group, etc.), alkenyl groups (vinyl group, arylgroup, etc.), cycloalkenyl groups (2-cyclopentene-1-yl,2-cyclohexane-1-yl groups, etc.), alkynyl groups (ethynyl group,propagyl group, etc.), aryl groups (phenyl group, p-tryl group, naphthylgroup, etc.), hetero ring groups (2-furyl group, 2-thienyl group,2-pyrimidinyl group, 2-benzothiazolyl group, etc.), cyano groups,hydroxyl groups, nitro groups, carboxyl groups, alkoxy groups (methoxygroup, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxygroup, 2-methoxyethoxy group, etc.), aryloxy groups (phenoxy group,2-methyl phenoxy group, 4-tert-butyl phenoxy group, 3-nitro phenoxygroup, 2-tetradecanoyl amino phenoxy group, etc.), acyloxy groups(formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group,benzoyloxy group, p-methoxyphenyl carbonyloxy group, etc.), amino groups(amino group, methyl amino group, dimethyl amino group, anilino group,N-methyl-anilino group, diphenyl amino group, etc.), acyl amino groups(formyl amino group, acetyl amino group, pivaloyl amino group, lauloylamino group, benzoyl amino group, etc.), alkyl and aryl sulfonyl aminogroups (methylsulfonyl amino group, butylsulfonyl amino group,phenylsulfonyl amino group, 2,3,5-trichlorophenyl sulfonyl amino group,p-methyl phenylsulfonyl amino group, etc.), mercapto groups, alkylthiogroups (methylthio group, ethylthio group, n-hexadecylthio group, etc.),arylthio groups (phenylthio group, p-chlorophenylthio group,m-methoxyphenylthio group, etc.), sulfamoyl groups (N-ethyl sulfamoylgroup, N-(3-dodecyloxy propyl)sulfamoyl group, N,N-dimethylsulfamoylgroup, N-acetylsulfamoil group, N-benzoylsulfamoyl group, N—(N′phenylcarbamoyl)sulfamoyl group, etc.), sulfo groups, acyl groups(acetyl group, pivaloylbenzoyl group, etc.) and carbamoyl groups(carbamoyl group, N-methylcarbamoyl group, N,N-dimethylcarbamoyl group,N,N-di-n-octylcarbamoyl group, N-(methylsulfonyl)carbamoyl group, etc.).

R₁, R₂ are preferably substituted or non-substituted phenyl groups orsubstituted or non-substituted cyclohexyl groups, more preferably phenylgroups including a substituent or cyclohexyl groups including asubstituent, further preferably phenyl groups including a substituent atposition 4 or cyclohexyl groups including a substituent at position 4.

R₃ is preferably a hydrogen atom, a halogen atom, an alkyl group, analkenyl group, a aryl group, a hetero ring group, a hydroxyl group, acarboxyl group, an alkoxy group, an aryloxy group, an acyloxy group, acyano group or an amino group, and further preferably a hydrogen atom, ahalogen atom, an alkyl group, a cyano group or alkoxy group.

Wa, Wb denote a hydrogen atom or a substituent.

(I) Wa and Wb may be bonded to each other to form a ring.

(II) At least one of Wa and Wb may have a ring structure, or

(III) At least one of Wa and Wb may be an alkenyl group or an alkynylgroup.

Specific examples of the substituents expressed by Wa and Wb may includehalogen atoms (fluorine atom, chloride atom, bromine atom, iodine atom,etc.), alkyl groups (methyl group, ethyl group, n-propyl group,isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group,etc.), cycloalkyl groups (cyclohexyl group, cyclopentyl group,4-n-dodecyl cyclohexyl group, etc.), alkenyl groups (vinyl group, arylgroup, etc.), cycloalkenyl groups (2-cyclopentene-1-yl,2-cyclohexane-1-yl groups, etc.), alkynyl groups (ethynyl group,propagyl group, etc.), aryl groups (phenyl group, p-tryl group, naphthylgroup, etc.), hetero ring groups (2-furyl group, 2-thienyl group,2-pyrimidinyl group, 2-benzothiazolyl group, etc.), cyano groups,hydroxyl groups, nitro groups, carboxyl groups, alkoxy groups (methoxygroup, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxygroup, 2-methoxyethoxy group, etc.), aryloxy groups (phenoxy group,2-methyl phenoxy group, 4-tert-butyl phenoxy group, 3-nitro phenoxygroup, 2-tetradecanoyl amino phenoxy group, etc.), acyloxy groups(formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group,benzoyloxy group, p-methoxyphenyl carbonyloxy group, etc.), amino groups(amino group, methyl amino group, dimethyl amino group, anilino group,N-methyl-anilino group, diphenyl amino group, etc.), acyl amino groups(formyl amino group, acetyl amino group, pivaloyl amino group, lauloylamino group, benzoyl amino group, etc.), alkyl and aryl sulfonyl aminogroups (methylsulfonyl amino group, butylsulfonyl amino group,phenylsulfonyl amino group, 2,3,5-trichlorophenyl sulfonyl amino group,p-methyl phenylsulfonyl amino group, etc.), mercapto groups, alkylthiogroups (methylthio group, ethylthio group, n-hexadecylthio group, etc.),arylthio groups (phenylthio group, p-chlorophenylthio group,m-methoxyphenylthio group, etc.), sulfamoyl groups (N-ethyl sulfamoylgroup, N-(3-dodecyloxy propyl)sulfamoyl group, N,N-dimethylsulfamoylgroup, N-acetylsulfamoil group, N-benzoylsulfamoyl group, N—(N′phenylcarbamoyl)sulfamoyl group, etc.), sulfo groups, acyl groups(acetyl group, pivaloylbenzoyl group, etc.) and carbamoyl groups(carbamoyl group, N-methylcarbamoyl group, N,N-dimethylcarbamoyl group,N, N-di-n-octylcarbamoyl group, N-(methylsulfonyl)carbamoyl group,etc.).

The above substituents may be replaced by the above groups.

(1) The following structure can be cited when Wa and Wb are bonded toeach other to form a ring.

When Wa and Wb are bonded to each other to form a ring, a compoundpreferably includes a nitrogen-containing 5-membered ring or asulfur-containing 5-membered ring and is particularly preferablyexpressed by the following general expression (1) or (2).

In the generation expression (1), A₁, A₂ independently denote —O—, —S—,—NRx- (Rx denotes a hydrogen atom or a substituent) or CO—. Examples ofthe substituent denoted by Rx are synonymous with the specific examplesof the substituents denoted by Wa, Wb. Rx is preferably a hydrogen atom,an alkyl group, an aryl group or a hetero ring group. In the generationexpression (1), X denotes a non-metal atom of a group 14 to 16. X ispreferably ═O, ═S, ═NRc or ═C(Rd)Re. Here, Rc, Rd and Re denotesubstituents and examples thereof are synonymous with the specificexamples of the substituents denoted by Wa, Wb. L₁, L₂, R₁, R₂, R₃ and nare synonymous with L₁, L₂, R₁, R₂, R₃ and n in the generationexpression (A).

In the generation expression (2), Q₁ denotes —O—, —S—, —NRy- (Ry denotesa hydrogen atom or a substituent), —CRaRb- (Ra and Rb denote a hydrogenatom or a substituent) or CO—. Here, Ry, Ra and Rb denote substituentsand examples thereof are synonymous with the specific examples of thesubstituents denoted by Wa, Wb.

Y denotes a substituent. Examples of the substituent denoted by Y aresynonymous with the specific examples of the substituents denoted by Wa,Wb. Y is preferably an aryl group, a hetero ring group, an alkenyl groupor an alkynyl group. A phenyl group, a naphtyl group, an anthryl group,a phenanthryl group, and a biphenyl group and the like can be cited asthe aryl group denoted by Y. A phenyl group and a naphtyl group arepreferable, and a phenyl group is more preferable.

Hetero ring groups including at least one heteroatom such as a nitrogenatom, an oxygen atom or a sulfur atom such as a furyl group, a prolylgroup, a thienyl group, a pyridinyl group, a thiazolyl group and abenzothiazolyl group can be cited as the hetero ring group. A furylgroup, a pyrrolyl group, a thienyl group, a pyridinyl group and athiazolyl group are preferable.

These aryl groups or hetero ring groups may include at least onesubstituent. Examples of the substituent may include a halogen atom, analkyl group having a carbon number of 1 to 6, a cyano group, a nitrogroup, an alkyl sulfinyl group having a carbon number of 1 to 6, analkyl sulfonyl group having a carbon number of 1 to 6, a carboxyl group,a fluoroalkyl group having a carbon number of 1 to 6, an alkoxyl grouphaving a carbon number of 1 to 6, an alkylthio group having a carbonnumber of 1 to 6, an N-alkyl amino group having a carbon number of 1 to6, an N,N-dialkyl amino group having a carbon number of 2 to 12, anN-alkyl sulfamoyl group having a carbon number of 1 to 6 and anN,N-dialkyl sulfamoyl group having a carbon number of 2 to 12.

L₁, L₂, R₁, R₂, R₃ and n are synonymous with L₁, L₂, R₁, R₂, R₃ and n inthe generation expression (A).

(2) A specific example of the generation expression (A) when at leastone of Wa and Wb has a ring structure is preferably the followinggeneration expression (3).

In the generation expression (3), Q₃ denotes ═N— or ═CRz- (Rz denotes ahydrogen atom or a substituent) and Q₄ denotes a non-metal atom of agroup 14 to 16. Z denotes a nonmetal atom group that forms a ringtogether with Q₃ and Q₄. The ring formed from Q₃, Q₄ and Z may befurther condensed with another ring. The ring formed from Q₃, Q₄ and Zis preferably a nitrogen-containing 5-membered ring or 6-membered ringcondensed with a benzene ring. L₁, L₂, R₁, R₂, R₃ and n are synonymouswith L₁, L₂, R₁, R₂, R₃ and n in the generation expression (A).

(3) When at least one of Wa and Wb is an alkenyl group or an alkynylgroup, it is preferably a vinyl group or an ethynyl group including asubstituent.

Out of the compounds expressed by the above generation expressions (1),(2) and (3), those expressed by the generation expression (3) areparticularly preferable.

The compounds expressed by the generation expression (3) are excellentin heat resistance and light resistance as compared with those expressedby the generation expression (1) and are good in solubility to anorganic solvent and compatibility with polymers as compared with thoseexpressed by the general expression (2).

The compound expressed by the general expression (A) of the presentinvention can be contained by adjusting an amount appropriate to impartdesired wavelength dispersion and oozing preventing property. Preferably1 to 15 mass % and particularly preferably 2 to 10 mass % of thecompound is added to the cellulose derivative. Within this range,sufficient wavelength dispersion and oozing preventing property can beimparted to the cellulose derivative of the present invention.

Note that the compounds expressed by the generation expressions (A),(1), (2) and (3) can be synthesized by referring to a known method.Specifically, they can be synthesized by referring to Journal ofChemical Crystallography (1997): 27(9); 512-526, Japanese UnexaminedPatent Publications Nos. 2010-31223 and 2008-107767, and the like.

(Cellulose Acylate)

A cellulose acylate film usable in the present invention mainly containscellulose acylate.

The cellulose acylate film usable in the present invention contains 60to 100 mass % of cellulose acylate to total 100 mass % of the film.Further, a total degree of acyl substitution of cellulose acylate is 2.0or higher and below 3.0 and more preferably 2.2 to 2.7.

Esters of celluloses and aliphatic carboxylic acids and/or aromaticcarboxylic acids having a carbon number of about 2 to 22 can be cited ascellulose acylate, and esters of celluloses and lower fatty acids havinga carbon number of 6 or smaller are particularly preferable.

An acyl group to be bonded to a hydroxyl group of cellulose may be astraight chain, may be branched or may form a ring. Further, it may bereplaced by another substituent. If the degree of substitution is thesame, birefringence is reduced when the aforementioned carbon number islarge. Thus, selection among acyl groups having a carbon number of 2 to6 is preferable, and the sum of a degree of propionyl substitution and adegree of butyryl substitution is 0.5 or higher. The carbon number ofthe cellulose acylate is preferably 2 to 4 and more preferably 2 to 3.

Specifically, mixed fatty acid esters of celluloses in which apropionate group, a butyrate group or a phthalyl group is bonded besidesan acetyl group such as cellulose acetate propionate, cellulose acetatebutyrate, cellulose acetate propionate or cellulose acetate phthalatecan be used as cellulose acylate. Note that a butyryl group formingbutyrate may be a straight chain or branched.

In the present invention, cellulose acetate, cellulose acetate butyrateor cellulose acetate propionate is particularly preferably used ascellulose acylate.

The cellulose acylate according to the present invention preferablysatisfies the following expressions (iii) and (iv) simultaneously.

2.0≦X+Y<3.0  Expression (iii)

0.5≦X  Expression (iv)

In the expressions, Y denotes a degree of substitution of acetyl groupand X denotes a degree of substitution of propionyl group or butyrylgroup or a mixture thereof.

To obtain optical properties suitable for purpose, resins havingdifferent degrees of substitution may be used by being mixed. A mixingratio at that time is preferably 1:99 to 99:1 (mass ratio).

Among those described above, cellulose acetate propionate isparticularly preferably used as cellulose acylate. In cellulose acetatepropionate, it is preferable that 0≦Y≦2.5 and 0.5≦X≦3.0 (however,2.0≦X+Y<3.0) and more preferably that 0.5≦Y≦2.0 and 1.0≦X≦2.0 (however,2.0≦X+Y<3.0). Note that the degree of acyl group substitution can bemeasured in accordance with ASTM-D817-96.

It is preferable that a number average molecular weight of celluloseacylate is in a range of 60000 to 300000 since the mechanical strengthof the obtained long stretched film is increased. More preferably,cellulose acylate having a number average molecular weight of 70000 to200000 is used.

A weight average molecular weight (Mw) and a number average molecularweight (Mn) of cellulose acylate are measured using gel permeationchromatography (GPC). Measurement conditions are as follows. Note thatthis measurement method can be also used as a measurement method forother polymers in the present invention.

-   -   Solvent: methylene chloride;    -   Column: three columns, Shodex K806, K805 and K803G (produced by        Showa Denko K.K.) are used;    -   Column temperature: 25° C.;    -   Sample Concentration: 0.1 mass %;    -   Detector: RI Model 504 (produced by GL Sciences Inc.);    -   Pump: L6000 (produced by Hitachi, Ltd.)    -   Flow rate: 1.0 ml/min    -   Calibration curve: Standard polystyrene STK, a calibration curve        by 13 samples of standard polystyrene (produced by Tosoh        Corporation) Mw=1000000 to 500 is used. 13 samples are used        substantially at equal intervals.

A remaining sulfur content in cellulose acylate is preferably in a rangeof 0.1 to 45 mass ppm in terms of sulfur element. These are thought tobe contained in the form of salts. If the remaining sulfur contentexceeds 45 mass ppm, there is a tendency to be fractured during thermalstretching and during slitting after thermal stretching. Note that theremaining sulfur content is more preferably in a range of 1 to 30 massppm. The remaining sulfur content can be measured by a method prescribedin ASTM D817-96.

A free acid content in cellulose acylate is preferably in a range of 1to 500 mass ppm. It is preferable that the free acid content is in theabove range since fracture is unlikely to occur as in the above case.Note that the free acid content is preferably in a range of 1 to 100mass ppm, which makes fracture more unlikely, and particularlypreferably in a range of 1 to 70 mass ppm. The free acid content can bemeasured by a method prescribed in ASTM D817-96.

It is preferable to cleanse the synthesized cellulose acylate moresufficiently than in the case of being used in a solution casting methodsince a remaining alkaline earth metal content, a remaining sulfurcontent and a remaining acid content can be set in the above ranges.

Further, cellulose acylate preferably contains few luminescent spotswhen being formed into the long stretched film. Luminescent spots meanpoints (spots) seen due to leaking light from an opposite side when twopolarizing plates are arranged in a cross Nicol state, an optical filmor the like is placed therebetween, light is emitted from the side ofone polarizing plate and observation is made from the side of the otherpolarizing plate. The luminescent spots having a diameter of 0.01 mm orlonger are preferably at a density of 200/cm² or less, more preferablyat a density of 100/cm² or less, further preferably at a density of50/cm² or less, even more preferably at a density of 30/cm² or less,particularly preferably at a density of 10/cm² or less and mostpreferably at a density of 0.

The luminescent spots having a diameter of 0.005 to 0.01 mm are alsopreferably at a density of 200/cm² or less, more preferably at a densityof 100/cm² or less, further preferably at a density of 50/cm² or less,even more preferably at a density of 30/cm² or less, particularlypreferably at a density of 10/cm² or less and most preferably at adensity of 0.

Raw material cellulose of cellulose acylate is not particularly limited,but cotton linter, wood pulp, kenaf and the like can be cited. Further,cellulose acylates obtained therefrom can be used while being mixed atan arbitrary ratio.

Cellulose acylate can be produced by a known method. Specifically, itcan be synthesized, for example, by referring to Japanese UnexaminedPatent Publication No. H10-45804.

Further, cellulose acylate is also affected by trace metal components incellulose acylate. These trace metal components are thought to berelated to water used in the production process. Less components whichcan become insoluble nuclei are preferable. Particularly, metal ions ofiron, calcium, magnesium and the like may form insoluble matters byforming salts with polymer decomposition products possibly containingorganic acid groups and, hence, few metal ions are preferable. Further,calcium (Ca) components easily form coordination compounds (i.e.complexes) with acid components such as carboxylic acid and sulfonicacid and many ligands and may form scum (insoluble sediments,turbidness) derived from lots of insoluble calcium and, hence, fewcalcium components are preferable.

Specifically, a content of iron (Fe) components in cellulose acylate ispreferably 1 mass ppm or less. Further, a content of calcium (Ca)components in cellulose acylate is preferably 60 mass ppm or less, andmore preferably 0 to 30 mass ppm. Furthermore, a content of magnesium(Mg) components in cellulose acylate is preferably 0 to 70 mass ppm, andparticularly preferably 0 to 20 mass ppm since an excessive contentproduces insoluble matters.

Note that the contents of metal components such as the content of iron(Fe) components, the content of calcium (Ca) components and the contentof magnesium (Mg) components can be analyzed using an ICP-AES (inductivecoupling plasma atomic emission spectrometer) after absolutely driedcellulose acylate is pre-treated by a micro digest wet decompositionapparatus (sulfuric and nitric acid decomposition) and alkaline melting.

(Additives)

The long stretched film obtained by the present invention may beappropriately mixed with polymer components other than cellulose esterto be described later. Polymer components to be mixed are preferablyexcellent in compatibility with cellulose ester and a transmissivitywhen the long stretched film is formed is 80% or higher, preferably 90%or higher and further preferably 92% or higher.

Examples of the additive to be added may include a plasticizer, anultraviolet absorbing agent, a retardation regulating agent, anantioxidant, a deterioration preventing agent, a release assistant, asurface-active agent, a dye, fine particles and the like. In thisembodiment, additives other than fine particles may be added inpreparing a cellulose ester solution or may be added in preparing a fineparticle dispersion liquid. A polarizing plate used in an image displaydevice such as an organic EL display is preferably added with aplasticizer, an antioxidant, an ultraviolet absorbing agent and the likethat impart heat resistance and moisture resistance.

These compounds are preferably contained in cellulose ester in a rangeof 1 to 30 mass % and preferably in a range of 1 to 20 mass %. Further,to suppress bleed-out and the like during stretching and drying,compounds preferably have a vapor pressure of 1400 Pa or lower at 200°C.

These compounds may be added together with cellulose ester and a solventin preparing the cellulose ester solution or may be added during orafter the preparation of the solution.

(Retardation Regulating Agent)

An aromatic compound having two or more aromatic rings as disclosed inEuropean Patent Publication No. 911,656A2 can be used as a compound tobe added to regulate retardation.

Further, two or more kinds of aromatic compounds may be used incombination. Aromatic rings of the aromatic compounds include aromatichetero rings in addition to aromatic hydrocarbon rings. The aromatichetero rings are particularly preferable and generally unsaturatedhetero rings. Among them, 1,3,5-triazine rings are particularlypreferable.

(Polymer or Oligomer)

A cellulose ester film in this embodiment preferably contains celluloseester and a polymer or oligomer of a vinyl-based compound including asubstituent selected from a carboxyl group, a hydroxyl group, an aminogroup, an amide group and a sulfo group and having a weight averagemolecular weight in a range of 500 to 200,000. A content mass ratio ofthe cellulose ester and the polymer or oligomer is preferably in a rangeof 95:5 to 50:50.

(Matting Agent)

In this embodiment, fine particles can be contained as a matting agentin the long stretched film, whereby the stretched film can be easilyconveyed and wound when being long.

The matting agent is preferably composed of primary or secondaryparticles having a particle diameter of 10 nm to 0.1 μm. A substantiallyspherical matting agent composed of primary particles having an aspectratio of 1.1 or lower is preferably used.

The fine particles preferably contain silicon and particularlypreferably silicon dioxide. Examples of silicon dioxide fine particlespreferable in this embodiment may include particles commerciallyavailable under the name of Aerosil R972, R972V, R974, R812, 200, 200V,300 R202, OX50, TT600 (produced by Nippon Aerosil Co., Ltd.), andAerosil 200V, R972, R972V, R974, R202 and R812 can be preferably used.Examples of polymer fine particles may include silicone resins,fluororesins and acrylic resins. Silicone resins are preferable andthose having a three-dimensional network structure are particularlypreferable, and examples thereof may include Tospearl 103, 105, 108,120, 145, 3120 and 240 (produced by Momentive Performance MaterialsInc.).

Silicon dioxide fine particles preferably have a primary averageparticle diameter of 20 nm or shorter and an apparent specific gravityof 70 g/L or more. An average diameter of the primary particles ispreferably 5 to 16 nm and further preferably 5 to 12 nm. An averagediameter of the primary particles is preferably small because of lowhaze. An apparent specific gravity is preferably 90 to 200 g/L or moreand more preferably 100 to 200 g/L or more. As the apparent specificgravity increases, it becomes possible to prepare a fine particledispersion liquid having a high concentration, which is preferable sincehaze does not occur and aggregates are not produced.

An added amount of the matting agent in this embodiment is preferably0.01 to 1.0 g, more preferably 0.03 to 0.3 g and further preferably 0.08to 0.16 g per 1 m² of the long stretched film.

(Other Additives)

Besides, a heat stabilizer such as inorganic fine particles such askaoline, talc, diatomaceous earth, quartz, calcium carbonate, bariumsulfate, titanium oxide and alumina and salts of alkaline earth metalssuch as calcium and magnesium may be added. Further, a surface-activeagent, a release assistant, an antistat, a flame retardant, a lubricant,oil and the like may be added.

A cellulose ester-based resin film usable in the present invention canbe formed by known methods, among which solution casting methods andmelt casting methods are preferable.

<Polycarbonate-Based Resin>

Next, polycarbonate-based resin is described.

Various polycarbonate-based resins can be used without beingparticularly limited. In terms of chemical properties and physicalproperties, aromatic polycarbonate resins are preferable and bisphenolA-based polycarbonate resins are particularly preferable. Among them,those using a bisphenol A derivative obtained by introducing a benzenering, a cyclohexane ring, an aliphatic hydrocarbon group and the likeinto bisphenol A are more preferable. Further, polycarbonate resinsobtained using a derivative obtained by introducing the above functionalgroups asymmetrically into a carbon in the center of bisphenol A andstructured to reduce anisotropy in a unit molecule are particularlypreferable. For example, polycarbonate resins obtained using bisphenol Ain which two methyl groups of a carbon in the center of bisphenol A arereplaced by a benzene ring, those obtained by replacing one hydrogen ofeach benzene ring of bisphenol A by a methyl group, a phenyl group orthe like asymmetrically with respect to a center carbon are particularlypreferable as such polycarbonate resins. Specific examples may includepolycarbonate resins obtained from 4,4′-dihydroxydiphenyl alkanes andhalogen substituents of these by a phosgene method ortransesterification such as 4,4′-dihydroxydiphenyl methane,4,4′-dihydroxydiphenyl ethane and 4,4′-dihydroxydiphenyl butane. Besidesthese, examples may include polycarbonate resins described in JapaneseUnexamined Patent Publications Nos. 2006-215465, 2006-91836,2005-121813, 2003-167121.

The polycarbonate resin may be used by being mixed with transparentresin such as polystyrene-based resin, methyl methacrylate-based resinand cellulose acetate-based resin. Further, a resin layer containingpolycarbonate resin may be laminated on at least one surface of a resinfilm formed using cellulose acetate-based resin.

The polycarbonate-based resin preferably has a glass transitiontemperature (Tg) of 110° C. or higher and a water absorption (valuemeasured in water of 23° C. for 24 hours) of 0.3% or lower. Thepolycarbonate-based resin more preferably has a Tg of 120° C. or higherand a water absorption of 0.2% or lower.

A polycarbonate-based resin film usable in the present invention can beformed by known methods, among which solution casting methods and meltcasting methods are preferable.

Next, a method for forming a thermoplastic resin film is described. Inthe following description, a method for forming a long film of celluloseester-based resin is described as an example.

<Solution Casting Method>

A solution casting method is preferable in terms of suppressing thecoloring of the film, foreign matter defects and optical defects such asdie lines and providing the flatness and transparency of the film.

(Organic Solvent)

Any organic solvent can be used without limitation as an organic solventuseful to form a dope in the case of forming the cellulose ester-basedresin film according to the present invention by the solution castingmethod as long as it can simultaneously dissolve cellulose acetate andother additives.

Examples of a chlorine containing organic solvent may include methylenechloride and examples of a chlorine-free organic solvent may includemethyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran,1,3-dioxolane, 1,4-dioxane, cyclohexane, ethyl formate,2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol,1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol,1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol andnitroethane. Methylene chloride, methyl acetate, ethyl acetate andacetone can be preferably used.

The dope preferably contains a straight or branched-chain aliphaticalcohol of 1 to 40 mass % having a carbon number of 1 to 4 besides theabove organic solvent. As a ratio of alcohol in the dope increases, aweb is gelled and easily peeled from a metal support. If the ratio ofalcohol is small, it also functions to promote the dissolution ofcellulose acetate in a chlorine-free organic solvent system.

Particularly, a dope composition is preferably obtained by dissolving atleast 15 to 45 mass % of acrylic resin, cellulose ester resin andacrylic particles in total in a solvent containing methylene chlorideand straight or branched-chain aliphatic alcohol having a carbon numberof 1 to 4.

Examples of the straight or branched-chain aliphatic alcohol having acarbon number of 1 to 4 may include methanol, ethanol, n-propanol,iso-propanol, n-butanol, sec-butanol and tert-butanol. Among these,ethanol is preferable in terms of dope stability, relative low boilingpoint and dryness.

(Solution Casting)

A solution casting method is composed of a step of preparing a dope bydissolving resin and additives in a solvent, a step of casting the dopeonto a belt-like or drum-like metal support, a step of drying the castdope as a web, a step of peeling the dope from the metal support, a stepof stretching or keeping a width, a step of further drying and a step ofwinding a finished long stretched film.

A high concentration of cellulose acetate in the dope is preferablesince a drying load after casting onto the metal support can be reduced.However, if the concentration of cellulose acetate is too high, a loadduring filtering increases to degrade filtering accuracy. Aconcentration capable of combining these is preferably 10 to 35 mass %and further preferably 15 to 25 mass %. The metal support in the castingstep preferably has a mirror-finished surface, and a stainless steelbelt or a drum having a surface plated by a casting is preferably usedas the metal support.

A surface temperature of the metal support in the casting step is set at−50° to a temperature at which the solvent is not boiled to foam. Ahigher temperature is preferable since the web can be dried at a fasterrate. However, if the temperature is too high, the web may be foamed orthe flatness thereof may be deteriorated.

A preferable support temperature is appropriately set in a range of 0 to100° C. and further preferably in a range of 5 to 30° C. Alternatively,it is also a preferable method to gel the web by cooling and peel theweb from the drum in a state containing a lot of remaining solvent. Amethod for controlling the temperature of the metal support is notparticularly limited. A method for blowing hot or cold air and a methodfor bringing hot water into contact with the underside of the metalsupport are known as such. The use of hot water is preferable since heatis efficiently transferred and, hence, a time until the temperature ofthe metal support becomes constant is short.

In the case of using hot air, hot air having a temperature not lowerthan a boiling point of the solvent and higher than a target temperaturemay be used while preventing foaming in consideration of a temperaturereduction of the web due to evaporation latent heat of the solvent.

Particularly, it is preferable to efficiently perform drying whilechanging the temperature of the support and the temperature of thedrying air during a period from casting to peeling.

In order for the cellulose ester-based resin film to exhibit goodflatness, a remaining solvent amount when the web is peeled from themetal support is preferably 10 to 150 mass %, further preferably 20 to40 mass % or 60 to 130 mass % and particularly preferably 20 to 30 mass% or 70 to 120 mass %.

The remaining solvent amount is defined by the following equation.

Remaining solvent amount (mass %)={(M−N)/N}×100

Note that M denotes a mass of a sample collected at an arbitrary pointof time during or after the production of the web or the long film and Ndenotes a mass after heating M at 115° C. for 1 hour.

Further, in the step of drying the cellulose-based resin film, the webis peeled from the metal support and further dried such that theremaining solvent amount is reduced to preferably 1 mass % or less,further preferably 0.1 mass % or less and particularly preferably 0 to0.01 mass % or less.

In the film drying step, a roll drying method (method for alternatelypassing a web through a multitude of rolls arranged at upper and lowersides) and a method for drying a web while conveying the web by a tentermethod are generally adopted.

<Melt Casting Method>

A melt casting method is a preferable film formation method in terms ofeasily reducing retardation Rt in a thickness direction after obliquestretching and providing excellent dimensional stability of the film dueto a small remaining volatile component amount. The melt casting methodmeans heating and melting a composition containing resin and additivessuch as a plasticizer to a temperature at which the composition exhibitsfluidity and, thereafter, casting a melt containing fluid celluloseacetate. Formation methods by melt casting can be classified into a meltextrusion molding method, a press molding method, an inflation method,an injection molding method, a blow molding method, a stretch moldingmethod and the like. Among these, the melt extrusion method capable ofproviding a long film excellent in mechanical strength and surfaceaccuracy is preferable.

A plurality of raw materials used in melt extrusion are preferablynormally kneaded and formed into pellets in advance.

Pellets may be formed by a known method. For example, pellets can beformed by supplying dry cellulose acetate, a plasticizer and otheradditives to a single- or double-screw extruder by a feeder, kneadingthem using the extruder, extruding the kneaded material in the form of astrand from a die, cooling the strand with water or air and cutting thestrand.

The additives may be mixed before being supplied to the extruder or maybe supplied by different feeders.

A small amount of additives such as particles and an antioxidant arepreferably mixed in advance for uniform mixing.

The extruder preferably works at a temperature which is as low aspossible and at which a shear force can be suppressed and pelletformation is possible in such a manner that the resin is not degraded(molecular weight reduction, coloring, gel production, etc.). Forexample, in the case of a double-screw extruder, two deep groove typescrews are preferably rotated in the same direction. An engaged type ispreferable in terms of kneading homogeneity.

A film is formed using the pellets obtained as described above. Ofcourse, a film can also be formed by supplying raw material powder as itis to the extruder by the feeder without forming pellets.

A melting temperature when the above pellets are extruded using asingle- or double-screw extruder is set at about 200 to 300° C., themelt is cast in the form of a film from a T-die after being filtered bya leaf-disc type filter or the like to remove foreign matters, and thefilm is nipped by a cooling roll and an elastic touch roll andsolidified on the cooling roll.

When being introduced into the extruder from a supply hopper, thepellets are preferably fed under vacuum or decompression or under aninert gas atmosphere to prevent oxidative decomposition and the like.

An extrusion flow rate is preferably stably controlled such as byintroducing a gear pump. Further, a stainless steel fiber sinteredfilter is preferably used as the filter used to remove foreign matters.The stainless steel fiber sintered filter is formed by compressing astainless steel fiber body in a complicatedly entangled state andsintering at contact positions to unite, and filtering accuracy can beadjusted by changing a density based on the thickness of fibers and acompression amount.

The additives such as the plasticizer and particles may be mixed withthe resin in advance or may be kneaded in the extruder. A mixing devicesuch as a static mixer is preferably used for uniform mixing.

A film temperature on the touch roller side when the film is nipped bythe cooling roll and the elastic touch roll is preferably set at Tg ofthe film or higher and Tg+110° C. or lower. A known roll can be used asthe roll having an elastic surface used for such a purpose.

The elastic touch roll is also called a compressive rotary body. Acommercially available one can be used as the elastic touch roll.

When the long film is peeled from the cooling roll, a tension ispreferably controlled to prevent the deformation of the long film.

The long film may be a single-layer film or a laminated film composed oftwo or more layers. The laminated film can be obtained by known methodssuch as a co-extrusion molding method, a co-casting molding method, afilm lamination method and a coating method. Among these, theco-extrusion molding method and the co-casting molding method arepreferable.

The long film formed by the above method is conveyed to the stretchingdevice described above and stretched in an oblique direction.

A thickness of the long film is preferably 20 to 400 μm and morepreferably 30 to 200 μm.

In the present invention, thickness unevenness σm in a flowing directionof the long film supplied to be stretched is below 0.30 μm, preferablybelow 0.25 μm and further preferably below 0.20 μm in terms of keeping atake-up tension of the long film at the entrance of the above obliquestretching tenter constant and stabilizing optical properties such asthe orientation angle and retardation. If the thickness unevenness σm inthe flowing direction of the long film is not below 0.30 μm, variationsof the optical properties of the long stretched film such as theretardation and orientation angle are notably deteriorated.

A long film having a thickness gradient in the width direction may besupplied as the long film. The thickness gradient of the long film canbe empirically obtained by experimentally stretching long films havingvarious thickness gradients such that a film thickness at a positionwhere stretching in a subsequent step is completed can be most uniform.The thickness gradient of the long film can be, for example, so adjustedthat a thicker end part is thicker than a thinner end part by about 0.5to 3%.

A width of the long film is not particularly limited, but can be set at500 to 4000 mm and preferably at 1000 to 2000 mm.

A preferable modulus of elasticity at a stretching temperature when thelong film is obliquely stretched is 0.01 MPa or higher and 5000 MPa orlower and further preferably 0.1 MPa or higher and 500 MPa or lower inYoung's modulus. If the modulus of elasticity is too low, a shrinkageratio during/after stretching decreases and it becomes difficult tounwrinkle. If the modulus of elasticity is too high, a tension appliedduring stretching increases and parts for holding the opposite side edgeparts of the long film need to be strengthened, which increases a loadapplied to the tenter in the subsequent step.

A non-oriented long film may be used or a long film oriented in advancemay be supplied as the long film. Further, if necessary, a widthwiseorientation distribution of the long film may be arched or bowed. Inshort, a state of orientation of the long film can be so adjusted as toattain a desired orientation of the long stretched film at a positionwhere stretching in the subsequent step is completed.

(Oblique Stretching Step)

The oblique stretching step is as already described. The long stretchedfilm after the oblique stretching step is obliquely stretched in adirection of an angle exceeding 0° and below 90° with respect to thewidth direction of the long film. The stretched long stretched film iswound in the subsequent winding step.

(Winding Step)

A winding device is provided at the exit of the oblique stretchingdevice. The winding device can finely control the take-up position andangle of the long stretched film and wind the long stretched film havingsmall variations of the film thickness and optical values by beingarranged in such a manner as to take up the long stretched film at apredetermined angle with respect to the stretching device. Thus, thewrinkling of the long stretched film can be effectively prevented and awinding property of the long stretched film is improved, wherefore thestretched film having a long length can be wound. In this embodiment, atake-up tension T (N/m) of the long film after stretching is preferablyadjusted in a range of 100 N/m<T<300 N/m and preferably in a range of150 N/m<T<250 N/m.

If the take-up tension is equal to or lower than 100 N/m, the longstretched film is likely to be slackened or wrinkled and the retardationand a profile of the orientation axis in the width direction tend to bedeteriorated. On the other hand, if the take-up tension is equal to orhigher than 300 N/m, a variation of the orientation angle in the widthdirection is deteriorated and widthwise take-up efficiency (take-upefficiency in the width direction) tends to be deteriorated.

Further, in this embodiment, a fluctuation of the above take-up tensionT is preferably controlled with an accuracy of below ±5% and preferablybelow ±3%. If the fluctuation of the above take-up tension T is notbelow ±5%, variations of optical properties in the width direction andflowing direction increase. A method for measuring a load applied to thefirst roll at the exit part of the tenter, i.e. a tension of the longstretched film and controlling a rotation speed of a take-up roll by ageneral PID control method so that the measured value is constant can becited as a method for controlling the fluctuation of the above take-uptension T in the above range. A method for attaching a load cell to abearing portion of a roll and measuring a load applied to the roll, i.e.a tension of a long stretched film can be cited as a method formeasuring the load. A known tension or compression type load cell can beused as the load cell.

The long film after stretching is released from the gripping tools,discharged from the exit of the tenter, successively wound on a windingcore (winding roll) to be formed into a rolled body of the longstretched film.

Further, it is desirable to trim the opposite ends (opposite sides) ofthe long stretched film for the purpose of cutting off grip marks on theopposite sides of the long stretched film gripped by the gripping toolsand obtaining a desired width.

The trimming may be performed at once or may be performed separately aplurality of times.

Further, after being wound, the long stretched film may be deliveredagain, the opposite ends thereof may be trimmed and the trimmed longstretched film may be wound again to form a rolled body of the longstretched film if necessary.

Further, a masking film may be placed on the long stretched film beforethe long stretched film is wound and simultaneously wound for thepurpose of preventing the blocking of the long stretched film or thelong stretched film may be wound while a tape or the like is bonded toat least one end, preferably both ends of the long stretched film. Themasking film is not particularly limited as long as it can protect thelong stretched film. For example, a polyethylene terephthalate film, apolyethylene film, a polypropylene film and the like can be cited assuch.

<Long Stretched Film>

The orientation angle of the long stretched film obtained by theproducing method of this embodiment is inclined in a range exceeding 0°and below 90° with respect to the winding direction. A specific valuecan be appropriately selected depending on an intended use. Forexamples, values such as 15°, 22.5°, 45°, 67.5° and 75° can be cited assuch.

A variation of the widthwise orientation angle of the long stretchedfilm obtained by the producing method of this embodiment is preferably0.6° or smaller and further preferably 0.4° or smaller in the width ofat least 1300 mm. If a circular polarizing plate is obtained by bondinga long stretched film having a variation of an orientation angleexceeding 0.6° to a polarizer and mounted in a self-luminous imagedisplay device such as an organic EL display, color unevenness may becaused at the time of displaying a black image.

A value of in-plane retardation of the long stretched film obtained bythe producing method of this embodiment is preferably 120 nm or largerand 160 nm or smaller and further preferably 130 nm or larger and 150 nmor smaller. By setting the value of the in-plane retardation in theabove range, outside light reflection can be suppressed and displayquality can be improved in the case of use as a phase difference film ofa circular polarizing plate for organic EL display.

A variation of the in-plane retardation of the long stretched filmobtained by the producing method of this embodiment is preferably 3 nmor less and further preferably 1 nm or less in a length of at least 1300mm in the width direction. By setting the variation of the in-planeretardation in the above range, color unevenness at the time ofdisplaying a black image can be suppressed in the case of use as a phasedifference film for organic EL display.

An optimal value is selected for the in-plane retardation of the longstretched film obtained by the producing method of this embodiment basedon the design of a display device in which the long stretched film is tobe used. Note that the in-plane retardation of the film is a valueobtained by multiplying a difference between a refractive index nx in anin-plane slow axis direction and a refractive index ny in a directionperpendicular to the slow axis in the plane by an average thickness d ofthe long stretched film ((nx−ny)×d).

A film thickness of the long stretched film obtained by the producingmethod of this embodiment is, for example, preferably 10 to 200 μm, morepreferably 10 to 60 μm and further preferably 10 to 35 μm in terms ofmechanical strength.

Further, thickness unevenness in the width direction is preferably 3 μmor smaller and more preferably 2 μm or smaller since it affects whetheror not the long stretched film can be wound.

<Circular Polarizing Plate>

In the circular polarizing plate of the present invention, a polarizingplate protection film, a polarizer, a λ/4 phase difference film (longstretched film obtained in the present invention) and an adhesive filmare laminated in this order, and an angle between a slow axis of the λ/4phase difference film and an absorption axis of the polarizer is 45°.

In the present invention, a long polarizing plate protection film, along polarizer and a long λ/4 phase difference film are preferablylaminated in this order.

The circular polarizing plate according to the present invention can beproduced by using stretched polyvinyl alcohol doped with iodine ordichroic dye as the polarizer and bonding the polarizer and the λ/4phase difference film.

A film thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μmand particularly preferably 5 to 20 μm.

The polarizing plate can be produced by a general method. The λ/4 phasedifference film after an alkali saponification treatment is preferablybonded to one surface of the polarizer fabricated by immersing andstretching a polyvinyl alcohol-based film in an iodine solution, using acomplete saponification type polyvinyl alcohol aqueous solution.

The polarizing plate can be formed by further bonding a release film toan opposite surface of the polarizing plate protection film of thispolarizing plate. The protection film and the release film are used forthe purpose of protecting the polarizing plate during the shipment ofthe polarizing plate, during the inspection of a product and the like.

Embodiment in Organic EL Display

Further, a λ/4 plate using the long stretched film of the embodiment ofthe present invention is particularly preferably used as a circularpolarizing plate used to prevent the reflection of a self-luminousdisplay device such as an organic EL display. The long stretched filmaccording to the embodiment of the present invention can provide adisplay device particularly excellent in tinge uniformity in the case ofuse in an organic EL display due to excellent direction (orientationangle) uniformity of the slow axis in the width direction.

FIG. 5 shows an example of the configuration of an organic EL display Dof the present invention. The present invention is not limited to this.

As shown in FIG. 5, the organic EL display D is formed by providing acircular polarizing plate, in which a polarizer F8 is sandwiched by aλ/4 phase difference film F7 and a protection film F9, on an organic ELelement successively including a metal electrode F2, a luminous layerF3, a transparent electrode (ITO or the like) F4 and a sealing layer F5on a substrate F1 using glass, polyimide and the like via an adhesivebath F6. A hardening layer is preferably laminated on the protectionfilm F8. The hardening layer functions not only to prevent a surface ofthe organic EL display from being scratched, but also to prevent warpagecaused by the circular polarizing plate. Further, an anti-reflectionlayer may be provided on the hardening layer. A thickness of the organicEL element itself is about 1 μm.

Generally, in an organic EL display, a metal electrode, a luminous layerand a transparent electrode are successively laminated on a transparentsubstrate to form an element (organic EL element) as a luminous body.Here, the luminous layer is a laminated body of various organic thinfilms and known to be composed of various combinations such a laminatedbody of a hole injection layer made of triphenyl amine derivative or thelike and a luminous layer made of a fluorescent organic solid such asanthracene, a laminated body of such a luminous layer and an electroninjection layer made of a perylene derivative or the like and alaminated body of these hole injection layer, luminous layer andelectron injection layer.

The organic EL display emits light under the principle that holes andelectrons are injected into the luminous layer by applying a voltage tothe transparent electrode and the metal electrode, energy generated byrecoupling of these holes and electrons excites fluorescent substancesand the excited fluorescent substances radiate light when returning to aground state. An intermediate recoupling mechanism is the same as ingeneral diodes. As can be expected from this, a current and emissionintensity exhibit strong nonlinearity associated with rectification inresponse to an applied voltage.

In the organic EL display, at least one electrode has to be transparentto extract light emitted from the luminous layer, and a transparentelectrode formed from a transparent conductor such as indium tin oxide(ITO) is normally used as a positive electrode. On the other hand, tofacilitate electron injection and increase emission efficiency, it isimportant to use a substance having a small work function as a negativeelectrode. Normally, metal electrodes such as Mg—Ag and Al—Li are usedas such.

In the organic EL display thus configured, the luminous layer is formedas a very thin film having a thickness of about 10 nm. Thus, theluminous layer also substantially completely transmits light similarlyto the transparent electrode. As a result, light incident on a surfaceof the transparent substrate, passing through the transparent electrodeand the luminous layer and reflected by the metal electrode comes out tothe surface side of the transparent substrate again when light is notemitted, wherefore a display surface of the organic EL display lookslike a mirror surface when being viewed from outside.

The circular polarizing plate formed from the long stretched filmproduced using the present invention is suitable for organic EL displaysin which such outside light reflection is particularly problematic.

Technical features of the above long stretched film producing method aresummarized below.

A method for producing a long stretched film according to one aspect ofthe present invention includes at least a step of forming a long filmmade of thermoplastic resin, an oblique stretching step of deliveringthe long film in a specific direction different from a winding directionof a long stretched film after stretching and obliquely stretching thelong film in a direction of an angle exceeding 0° and below 90° withrespect to a width direction while gripping and conveying opposite endparts of the long film by a plurality of gripping tools of an obliquestretching device and a winding step of winding the long stretched filmafter the oblique stretching step, wherein the oblique stretching deviceincludes gripping tool travel support tools at opposite sides of thetraveling long film, each of the gripping tool travel support tools atthe opposite sides includes a plurality of gripping tools, the samenumber of the gripping tools are provided at the opposite sides, and acombination of the gripping tools forming a gripping tool pair isconstantly the same at grip start points where the long film is grippedby the gripping tools.

According to this configuration, the gripping tool returned to the gripstart point after releasing the long stretched film can form thegripping tool pair again with the same gripping tool paired duringstretching last time in the present invention. Further, since thegripping tools constituting the gripping tool pair are abraded or wornsubstantially to the same extent, the quality of the obtained longstretched film is less affected and the long stretched film can beprovided which has a small variation of an orientation angle in thewidth direction in an obliquely stretched state.

In the oblique stretching step of the above producing method, travelroute lengths and traveling speeds at the opposite sides per lap fromthe grip start points where the long film is gripped by the plurality ofgripping tools of the gripping tool travel support tools at an entranceside of the oblique stretching device to the grip start points at theentrance side of the oblique stretching device by way of grip releasepoints where the long film is released are preferably equal. Accordingto this configuration, the gripping tool traveling at an equal speed canconstantly form the gripping tool pair with the same gripping tool asthe one paired at first in the present invention. As a result, avariation of the orientation angle in the width direction caused bycombinations of the gripping tools constituting the gripping tool pairsbeing different in each lap can be prevented.

In the oblique stretching step of the above producing method, thetraveling speeds of the gripping tools are preferably increased anddecreased until the gripping tools grip the long film again afterreleasing the long stretched film so that the gripping tools of the samecombination are aligned at the grip start points. According to thisconfiguration, by adjusting the traveling speeds of the gripping tools,the entire lengths of the gripping tool travel support tools need not beequal and a drastic design change of the device is not necessary.Further, how much the speeds of the gripping tools need to be adjustedcan be calculated in advance when patterns of the gripping tool travelsupport tools and a stretching angle are adjusted. As a result, in theproducing method of the present invention, in the case of changing thestretching angle or the like, such a change can be immediately dealtwith and the gripping tools can be so adjusted that the same grippingtool pairs are constantly aligned at the grip start points, which isconvenient.

In the oblique stretching step of the above producing method, a straightline connecting the grip release points where the gripping tools releasethe long stretched film is preferably parallel to the width direction ofthe long stretched film. According to this configuration, stressesapplied to the long stretched film are cancelled out at oppositewidthwise end parts of the long stretched film when the gripping toolsrelease the long stretched film at the grip release points, whereforethickness unevenness of the obtained long stretched film is reduced.

In the above producing method, an in-plane retardation of the longstretched film is preferably 120 to 160 nm. According to thisconfiguration, outside light reflection can be suppressed and imagedisplay quality is improved in the case of use as a circular polarizingplate for organic EL display.

In the above producing method, the thermoplastic resin used for the longstretched film is preferably norbornene-based resin. According to thisconfiguration, since a stretching stress is low, the end parts of thelong stretched film are less likely to be wrinkled or shifted and avariation of the orientation angle in the width direction can besuppressed also when the long stretched film is conveyed at a highspeed.

In the above producing method, a film thickness of the obtained longstretched film is preferably 10 to 35 μm. If the film thickness of theobtained long stretched film is in the above range, sensitivity to thevariation of the orientation angle in the width direction is reduced andthe variation of the orientation angle in the width direction can bereduced.

A long stretched film according to another aspect of the presentinvention is characterized by being produced by the above long stretchedfilm producing method. Since this long stretched film is produced by theabove producing method, a variation of an orientation angle in a widthdirection is small.

EXAMPLES

The present invention is specifically described by way of the followingexamples. The present invention is not limited to these.

<Production of Long Film>

In the film forming step, long films A to C were produced by thefollowing method.

(Long Film A1)

The long film A1 was a cycloolefin-based resin film and produced by thefollowing producing method.

After 1.2 mass parts of 1-hexane, 0.15 mass parts of dibutyl ether and0.30 mass parts of triisobutylaluminum were poured into a reactor andmixed with 500 mass parts of dehydrated cyclohexane at a roomtemperature under a nitrogen atmosphere, a norbornene-based monomermixture containing 20 mass parts of tricyclo[4.3.0.12,5]deca-3,7-diene(dicyclopentadiene, hereinafter, abbreviated as DCP), 140 mass parts of1,4-methano-1,4,4a,9a-tetrahydrofluorene (hereinafter, abbreviated asMTF) and 40 mass parts of8-methyl-tetracyclo[4.4.0.12,5.17,10]-dodeca-3-ene (hereinafter,abbreviated as MTD) and 40 mass parts of tungsten hexachloride (0.7%toluene solution) were continuously added and polymerized for 2 hourswhile being kept at 45° C. 1.06 mass parts of butyl glycidyl ether and0.52 mass parts of isopropyl alcohol were added to the polymerizationsolution to inactivate a polymerization catalyst and stop apolymerization reaction.

Subsequently, 270 mass parts of cyclohexane was added to 100 mass partsof the obtained reaction solution containing a ring-opening polymer.After 5 mass parts of nickel-alumina catalyst (produced by JGC C&C) as ahydrogenation catalyst was further added, pressurized to 5 MPa byhydrogen and heated to 200° C. under stirring, the mixture was allowedto react for 4 hours to obtain a reaction solution containing 20% ofDCP/MTF/MTD ring-opening polymer hydrogenated polymer.

After the hydrogenation catalyst was removed by filtering, soft polymer(produced by Kuraray Co., Ltd.; Septon 2002) and antioxidant (producedby Ciba Specialty Chemicals; Irganox 1010) were respectively added toand dissolved in the obtained solution (0.1 mass part per 100 mass partsof the polymer for both). Subsequently, cyclohexane as a solvent andother volatile components were removed from the solution using acylindrical concentration dryer (produced by Hitachi Ltd.) and thehydrogenated polymer was extruded in a molten state in the form of astrand from an extruder, and formed into pellets and collected afterbeing cooled. When a copolymerization ratio of each norbornene-basedmonomer in the polymer was calculated from a remaining composition ofnorbornenes in the solution after polymerization (by a gaschromatography method), it was DCP/MTF/MTD=10/70/20 which wassubstantially equal to charge composition. A weight average molecularweight (Mw) of this ring-opening polymer hydrogenated product was31,000, a molecular distribution (Mw/Mn) thereof was 2.5, ahydrogenation rate thereof was 99.9% and Tg thereof was 134° C.

The obtained pellets of the ring-opening polymer hydrogenated productwere dried at 70° for 2 hours to remove moisture using a hot air dryerin which air was allowed to flow. Subsequently, the pellets were moldedby melt extrusion to form a cycloolefin polymer film having a thicknessof 75 μm using a single-screw extruder (produced by Mitsubishi HeavyIndustries, Ltd.; screw diameter was 90 mm, T-die lip was made oftungsten carbide, peel strength from molten resin was 44 N) having acoat hanger type T-die. Extrusion molding was performed in a clean roomwith a class of 10,000 or less on molding conditions, i.e. a moltenresin temperature of 240° C. and a T-die temperature of 240° C. toobtain the long film A1 having a length of 1000 mm.

(Long Film A2)

The long film A2 was obtained in the same manner as for the long film A1except that a die gap of the T-die lip was appropriately adjusted toattain a thickness of 35 μm after melt extrusion molding in the methodfor producing the long film A1.

(Long Film B1)

The long film B1 was a cellulose ester-based resin film and produced bythe following producing method.

<Fine Particle Dispersion Liquid>

Fine particles (Aerosil R972V produced by 11 mass parts Nippon AerosilCo., Ltd.) Ethanol 89 mass parts

The above were dispersed by a Manton-Gaulin homogenizer after beingstirred and mixed for 50 minutes by a dissolver.

<Fine Particle Additive Liquid>

Based on the following composition, the above fine particle dispersionliquid was slowly added into a dissolution tank containing methylenechloride while being sufficiently stirred. The dispersion liquid wasfurther dispersed by an Attritor so that the particle diameter ofsecondary particles became a predetermined size. This was filtered usinga Fine Met NF produced by Nippon Seisen Co., Ltd. to prepare a fineparticle additive liquid.

Methylene chloride 99 mass parts Fine particle dispersion liquid 1  5mass parts

<Main Dope Solution>

A main dope solution of the following composition was prepared. First,methylene chloride and ethanol were added into a pressure dissolutiontank. Cellulose acetate was poured into the pressure dissolution tankcontaining a solvent while being stirred. This was heated and completelydissolved while being stirred. This was filtered using Azumi FilterPaper No. 244 produced by Azumi Filter Paper Co., Ltd. to prepare themain dope solution. Note that compounds synthesized by the followingsynthesis examples were used as a sugar ester compound and an estercompound. Further, the following compound was used as a compound (B).

<Composition of Main Dope Solution>

Methylene Chloride 340 mass parts Ethanol 64 mass parts Celluloseacetate propionate (acetyl group 100 mass parts substitution degree of1.39, propionyl group substitution degree of 0.50, total substitutiondegree of 1.89) Compound (B) 5.0 mass parts Sugar ester compound 5.0mass parts Ester compound 2.5 mass parts Fine particle additive liquid 11 mass part [Chemical Formula 6]

(Synthesis of Sugar Ester Compound)

A sugar ester compound was synthesized by the following process.

[Chemical Formula 7]

R (SUBSTITUTION NUMBER) EXEMPLIFIED COMPOUND A-1 —H   (0)

  (8) EXEMPLIFIED COMPOUND A-2 —H   (1)

  (7) EXEMPLIFIED COMPOUND A-3 —H   (2)

  (6) EXEMPLIFIED COMPOUND A-4 —H   (3)

  (5) EXEMPLIFIED COMPOUND A-5 —H   (4)

  (4)

34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of anhydrous benzoicacid, 379.7 g (4.8 mol) of pyridine were charged into a four-head flaskprovided with a stirring device, a reflux cooler, a thermometer and anitrogen gas inlet pipe and heated while nitrogen gas was bubbled fromthe nitrogen gas inlet pipe under stirring, and an esterificationreaction was carried out at 70° C. for 5 hours.

Subsequently, the inside of the flask was decompressed to 4×10² Pa orless. After excess pyridine was distilled away at 60° C., the inside ofthe flask was decompressed to 1.3×10 Pa or less and heated to 120° C.,thereby distilling away most of anhydrous benzoic acid and producedbenzoic acid.

Finally, 100 g of water was added to a collected toluene layer. Afterbeing washed with water at an ambient temperature for 30 minutes, thetoluene layer was collected and toluene was distilled away at 60° C.under decompression (4×10² Pa or less), thereby obtaining a mixture ofcompounds A-1, A-2, A-3, A-4 and A-5 (sugar ester compound).

When the obtained mixture was analyzed by HPLC and LC-MASS, there were1.3 mass % of A-1, 13.4 mass % of A-2, 13.1 mass % of A-3, 31.7 mass %of A-4 and 40.5 mass % of A-5. An average degree of substitution was5.5.

<Measurement Conditions of HPLC-MS>

1) LC Part

-   -   Device: column oven (JASCO CO-965), detector (JASCO UV-970-240        nm), pump (JASCO PU-980), degasser (JASCO DG-980-50) produced by        Jasco Corporation    -   Column: Inertsil ODS-3, particle diameter of 5 μm, 4.6×250 mm        (produced by GL Sciences Inc.)    -   Column Temperature: 40° C.    -   Flow velocity: 1 ml/min    -   Mobile Phase: THF (1% acetic acid): H₂O (50:50)    -   Injection amount: 3 μl

2) MS Part

-   -   Device: LCQ DECA (Produced by Thermo Quest)    -   Ionization method: electrospray ionization (ESI) method    -   Spray voltage: 5 kV    -   Capillary temperature: 180° C.    -   Vaporizer temperature: 450° C.

(Synthesis of Ester Compound)

An ester compound was synthesized by the following process.

251 g of 1,2-propylene glycol, 278 g of anhydrous phthalic acid, 91 g ofadipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanateas an esterification catalyst were charged into a four-mouth flask of 2L provided with a thermometer, a stirrer and a reflux cooling pipe andgradually heated until 230° C. was reached in a nitrogen gas flow whilebeing stirred. A dehydration condensation reaction was carried out for15 hours and unreacted 1,2-propylene glycol was decompressed anddistilled away at 200° C. after the reaction was finished, whereby anester compound was obtained. The ester compound included an ester ofbenzoic acid at an end of a polyester chain formed by the condensationof 1,2-propylene glycol, anhydrous phthalic acid and adipic acid. Anacid number of the ester compound was 0.10 and a number averagemolecular weight thereof was 450.

Subsequently, using an endless belt casting device, the ester compoundwas uniformly cast onto a stainless steel belt support.

In the endless belt casting device, the above main dope solution wasuniformly cast onto the stainless steel belt support. A solvent wasevaporated on the stainless steel belt support until a remaining solventamount in the cast long film became 75%, the long film was peeled fromthe stainless steel belt support, and the drying of the long film wasfinished while the long film was conveyed by a multitude of rolls,whereby the long film B1 having a width of 1000 mm was obtained. A filmthickness of the long film B1 at this time was 100 μm.

(Long Film B2)

The long film B2 was obtained in the same manner as for the long film B1except that a film thickness during casting was appropriately adjustedso that a thickness after a drying step became 50 μm in the method forproducing the long film B1.

(Long Film C)

The long film C was a polycarbonate-based resin film and produced by thefollowing method.

<Dope Composition>

Polycarbonate resin (viscosity average molecular weight 100 mass partsof 40,000, bisphenol A type)2-(2′hydroxy-3′,5′-di-t-butylphenyl)-benzotriazol  1.0 mass partMethylene chloride 430 mass parts Methanol  90 mass parts

The above composition was poured into a sealed container and completelydissolved while being kept at 80° C. under pressure and stirred, wherebya dope composition was obtained.

Subsequently, this dope composition was filtered, cooled and kept at 33°C., uniformly cast onto a stainless steel band and dried at 33° C. for 5minutes. Thereafter, a drying time was adjusted at 65° C. to attain aretardation of 5 nm. After being peeled from the stainless steel band,the drying was completed while the dope composition was conveyed by amultitude of rolls, whereby the long film C1 having a film thickness of85 μm and a width of 1000 mm was obtained.

(Long Film C2)

The long film C2 was obtained in the same manner as for the long film C1except that a film thickness during casting was appropriately adjustedso that a thickness after melting became 40 μm in the method forproducing the long film C1.

<Production of Long Stretched Film>

In the oblique stretching step and the winding step, the long films A1to C2 were stretched and wound into a roll by oblique stretching devices(T1 to T5) adjusted to satisfy the following conditions.

(Stretching Device T1)

The stretching device T1 is shown in FIG. 2. In the stretching deviceT1, each gripping tool travel support tool includes the same number ofgripping tools (a total of 800). The angle (stretching angle) betweenthe delivering direction of the long film and the winding direction wasset at 47°. The length of the route of the inner gripping tool travelsupport tool Ri from the grip start point to the grip release point was18 m and the entire length was 43 m. The length of the route of theouter gripping tool travel support tool Ro from the grip start point tothe grip release point was 19 m and the entire length was 43 m.Specifically, the entire length of the route of the inner gripping tooltravel support tool Ri and that of the route of the outer gripping tooltravel support tool Ro were equal. The straight line connecting the griprelease points of the stretching device T1 was not parallel to the widthdirection of the long stretched film and the angle θ was 63°.

End parts of the long stretched film discharged from the stretchingdevice T1 were trimmed so that the final width of the long stretchedfilm became 1600 mm. Thereafter, the long stretched film was wound intoa roll with a take-up tension of 200 (N/m) by the winding deviceprovided at the exit.

(Stretching Device T2)

The stretching device T2 is shown in FIG. 3. The stretching device T2 isconfigured similarly to the stretching device T1 except that thepatterns of the gripping tool travel support tools were so adjusted thatthe straight line connecting the grip release points became parallel tothe width direction of the long stretched film.

(Stretching Device T3)

The stretching device T3 is shown in FIG. 4. In the stretching deviceT3, the entire length of the route of the outer gripping tool travelsupport tool Ro is longer than that of the route of the inner grippingtool travel support tool Ri. Further, the stretching device T3 isconfigured similarly to the stretching device T1 except in adopting thespeed adjusting mechanism for increasing the traveling speed of thegripping tools having released the grip at the grip release point in theroute of the outer gripping tool travel support tool Ro. Specifically,the stretching device D3 is so formed that the entire length of theroute of the inner gripping tool travel support tool Ri is 44 m andshorter than that of the route of the outer gripping tool travel supporttool Ro (45 m). Thus, there is a possibility that the combinations ofthe gripping tools constituting the gripping tool pairs change in eachlap. Therefore, the speed of the gripping tools having released the gripis increased in the route of the outer gripping tool travel support toolRo for adjustment so that the gripping tools constantly form thegripping tool pairs with the same gripping tools paired last time.

(Stretching Device T4)

A stretching device T4 (not shown) is configured similarly to thestretching device T3 except that the patterns of the gripping tooltravel support tools are adjusted so that the straight line connectingthe grip release points becomes parallel to the width direction of thelong stretched film.

(Stretching Device T5)

The stretching device T5 is shown in FIG. 6. As shown in FIG. 6, in thestretching device T5, the entire length of the route of the innergripping tool travel support tool Ri is longer than that of the route ofthe outer gripping tool travel support tool Ro. Specifically, the entirelength of the route of the inner gripping tool travel support tool Riand that of the route of the outer gripping tool travel support tool Roare not equal. Further, the straight line B connecting the grip releasepoints is not parallel to the width direction of the long film F.Specifically, an angle θc between the straight line B and the travelingdirection of the long stretched film F is 62°. Further, the route of theinner gripping tool travel support tool Ri includes 830 gripping tools 1and the route of the outer gripping tool travel support tool Ro includes780 gripping tools 1. Specifically, the number of the gripping toolsprovided in the route of the inner gripping tool travel support tool Riand that of the gripping tools provided in the route of the outergripping tool travel support tool Ro are not equal.

Examples 1 to 12, Comparative Examples 1 to 3

Based on combinations shown in TABLE-1, the long films A1 to C1 werestretched by the stretching devices T1 to T5 to produce long stretchedfilms 1 to 15 (Examples 1 to 12, Comparative Examples 1 to 3). Thetraveling speed of the gripping tools at this time was set at 20 m/min.

Further, temperature conditions of a tenter oven when the long film Awas used were adjusted as follows: 140° C. in the preheating zone, 140°C. in the stretching zone, 137° C. in the thermal fixing zone and 80° C.in the cooling zone. Further, temperature conditions of the tenter ovenwhen the long film B was used were adjusted as follows: 180° C. in thepreheating zone, 180° C. in the stretching zone, 177° C. in the thermalfixing zone and 90° C. in the cooling zone. Further, temperatureconditions of the tenter oven when the long film C was used wereadjusted as follows: 160° C. in the preheating zone, 160° C. in thestretching zone, 157° C. in the thermal fixing zone and 80° C. in thecooling zone.

Examples 13 to 18, Comparative Examples 4 to 6

Based on combinations shown in TABLE-2, the long films A1 to C1 werestretched by the stretching devices T2, T4 and T5 to produce longstretched films 16 to 24 (Examples 13 to 18, Comparative Examples 4 to6). The traveling speed of the gripping tools at this time was set at100 m/min. Further, temperature conditions of the tenter oven when thelong film A was used were adjusted as follows: 150° C. in the preheatingzone, 148° C. in the stretching zone, 144° C. in the thermal fixing zoneand 90° C. in the cooling zone. Further, temperature conditions of thetenter oven when the long film B was used were adjusted as follows: 187°C. in the preheating zone, 187° C. in the stretching zone, 181° C. inthe thermal fixing zone and 950° C. in the cooling zone. Further,temperature conditions of the tenter oven when the long film C was usedwere adjusted as follows: 166° C. in the preheating zone, 166° C. in thestretching zone, 164° C. in the thermal fixing zone and 90° C. in thecooling zone.

Examples 19 to 24, Comparative Examples 7 to 9

Based on combinations shown in TABLE-3, the long films A2 to C2 werestretched by the stretching devices T2, T4 and T5 to produce longstretched films 25 to 33 (Examples 19 to 24, Comparative Examples 7 to9). The traveling speed of the gripping tools at this time was set at 20m/min.

Example 25

A polyvinyl alcohol film having a thickness of 120 μm was uniaxiallystretched (temperature of 110° C., stretch ratio of 5).

This was immersed in an aqueous solution containing 0.075 g of iodine, 5g of potassium iodide and 100 g of water for 60 seconds and,subsequently, immersed in an aqueous solution of 68° C. containing 6 gof potassium iodide, 7.5 g of boric acid and 100 g of water. This waswashed with water and dried to obtain a polarizer.

The produced long stretched film 1 was bonded to one surface of theabove polarizer using a 5% aqueous solution of polyvinyl alcohol as anadhesive. At that time, the film was so bonded that a transmission axisof the polarizer and a slow axis of the produced long stretched film(λ/4 phase difference film) form 45°. A Konica Minolta tack film KC6UA(produced by Konica Minolta Opto Products Co., Ltd.) was similarlybonded to the other surface of the polarizer after an alkalisaponification treatment to produce the circular polarizing plate 1.

(Production of Organic EL Display)

A reflecting electrode made of chromium and having a thickness of 80 nmwas formed on a glass substrate by sputtering, ITO (indium tin oxide)was formed into a film having a thickness of 40 nm as a positiveelectrode on the reflecting electrode by sputtering,poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) wasformed into a hole transport layer having a thickness of 80 nm on thepositive electrode by sputtering, and luminous layers of RGB having afilm thickness of 100 nm were formed on the hole transport layer using ashadow mask.

Tris(8-hydroxynolinato)aluminum (Alq₃) as a host and a light-emittingcompound[4-(dicyanomethylene)-2-methyl-6(p-dimethylaminostyryl)-4H-pyran] (DCM)were co-deposited (mass ratio of 99:1) to form a red luminous layerhaving a thickness of 100 nm. Alq₃ as a host and a light-emittingcompound Coumarin 6 were co-deposited (mass ratio of 99:1) to form agreen luminous layer having a thickness of 100 nm. BAlq shown below as ahost and a light-emitting compound Perylene were co-deposited (massratio of 90:10) to form a blue luminous layer having a thickness of 100nm.

Further, a film of calcium having a thickness of 4 nm was formed as afirst negative electrode, into which electrons can be efficientlyinjected and which has a low work function, on the luminous layers byvacuum deposition, and a film of aluminum having a thickness of 2 nm wasformed as a second negative electrode on the first negative electrode.Here, aluminum used as the second negative electrode functions toprevent chemical alteration of calcium as the first negative electrodewhen a transparent electrode is formed on the second negative electrodeby sputtering. An organic luminous layer was obtained in this way.Subsequently, a transparent conductive film having a thickness of 80 nmwas formed on the negative electrode by sputtering. Here, ITO was usedas the transparent conductive film. Further, a film of silicon nitridehaving a thickness of 200 nm was formed as an insulating film on thetransparent conductive film by a CVD method (chemical depositionmethod).

A light emission area of the formed organic EL element was 1296 mm×784mm. Further, a front luminance when a direct-current voltage of 6 V wasapplied to this organic EL element was 1200 cd/m². The front luminancewas measured by measuring a 2-degree viewing angle front luminance in avisible light wavelength range of 430 to 480 nm such that an opticalaxis of a spectral radiance meter coincides with a normal from a lightemitting surface using the spectral radiance meter (CS-1000) produced byKonica Minolta Sensing Inc. and calculating an integrated intensity.

The circular polarizing plate 1 was so fixed onto the insulating film ofthe formed organic EL element using an adhesive that a surface of theproduced long stretched film (λ/4 phase difference film) faces a surfaceof the insulating film, thereby forming the organic EL display 1(Example 25).

Examples 26 to 48, Comparative Examples 10 to 18

By a method similar to Example 25, circular polarizing plates 2 to 33and organic EL displays 2 to 33 were produced using long stretched films2 to 33 (Examples 26 to 48, Comparative Examples 10 to 18). The usedlong stretched films and the obtained organic EL displays are shown inTABLE-4 and TABLE-5.

Reference Example 1

A polarizing plate on a visible side of a commercially available liquidcrystal display panel (produced by Sony Corporation: BRAVIA KDL-26J5)was peeled and bonded to the formed circular polarizing plate 13,thereby producing a liquid crystal panel 201. Subsequently, the liquidcrystal panel was set in a liquid crystal television to produce a liquidcrystal display device 301.

Reference Examples 2 and 3

Liquid crystal display devices 302 and 303 were produced in the samemanner as in the production of the above liquid crystal display device301 except that the circular polarizing plate 13 was changed to thecircular polarizing plates 14 and 15. The used long stretched films andobtained liquid crystal display devices are shown in TABLE-6.

<Evaluation>

The obtained long stretched films were evaluated as follows.

(Orientation Angle and Variation of Orientation Angle in WidthDirection)

Orientation angles of the produced long stretched films 1 to 33 weremeasured using a phase difference measuring device (KOBRA-WXK producedby Oji Scientific Instruments). As an evaluation method, the longstretched film was measured at an interval of 50 mm in the film widthdirection of the long stretched film and an average of the total datawas calculated. Further, a difference between a maximum value and aminimum value of all measurement values was evaluated as a variation ofthe orientation angle in the width direction.

(Evaluation Criteria of Variation of Orientation Angle in WidthDirection)

-   -   ⊚: Variation of the orientation angle in the width direction is        below 0.4°    -   ◯: Variation of the orientation angle in the width direction is        equal to or above 0.4° and below 0.6°    -   Δ: Variation of the orientation angle in the width direction is        equal to or above 0.6° and below 1.0°    -   x: Variation of the orientation angle in the width direction is        equal to or above 1.0°

(In-Plane Retardation and Widthwise Distribution of In-PlaneRetardation)

In-plane retardations of the produced long stretched films 1 to 33 weremeasured using the phase difference measuring device (KOBRA-WXK producedby Oji Scientific Instruments). As an evaluation method, the longstretched film was measured at an interval of 50 mm in the film widthdirection of the long stretched film and an evaluation was carried out.

The obtained organic EL displays and liquid crystal display devices wereevaluated as follows.

(Color Unevenness)

Color unevenness on the entire display in black display in the aboveproduced organic EL displays and liquid crystal display devices wasvisually evaluated based on the following criteria.

(Evaluation Criteria on Color Unevenness)

-   -   ⊚: Tinge does not differ from position to position on the        produced organic EL device or liquid crystal display device.    -   ◯: Tinge differs from position to position on the produced        organic EL display or liquid crystal display device, but such a        difference is not problematic in use.    -   Δ: Tinge differs from position to position on the produced        organic EL display or liquid crystal display device, and the        organic EL display or liquid crystal display device cannot be        used as a product.    -   x: Tinge largely differs from position to position on the        produced organic EL device or liquid crystal display device, and        the organic EL display or liquid crystal display device cannot        be used as a product.

The summary of the above various long stretched films, organic ELdisplays and liquid crystal display device and results of variousevaluations are collectively shown in TABLE-1 to TABLE-6.

TABLE-1 Used Film Orientation Variation of Obtained Long Stretching UsedLong Stretch Thickness Angle In-Plane Re Widthwise Stretched Film DeviceFilm Ratio (μm) (°) (nm) Orientation Angle Example 1 Long Stretched Film1 T1 A1 2.0x 52 45 140 ◯ Example 2 Long Stretched Film 2 T1 B1 2.0x 5245 140 ◯ Example 3 Long Stretched Film 3 T1 C1 2.0x 52 45 140 ◯ Example4 Long Stretched Film 4 T2 A1 2.0x 52 45 140 ⊚ Example 5 Long StretchedFilm 5 T2 B1 2.0x 52 45 140 ⊚ Example 6 Long Stretched Film 6 T2 C1 2.0x52 45 140 ⊚ Example 7 Long Stretched Film 7 T3 A1 2.0x 52 45 140 ◯Example 8 Long Stretched Film 8 T3 B1 2.0x 52 45 140 ◯ Example 9 LongStretched Film 9 T3 C1 2.0x 52 45 140 ◯ Example 10 Long Stretched Film10 T4 A1 2.0x 52 45 140 ⊚ Example 11 Long Stretched Film 11 T4 B1 2.0x52 45 140 ⊚ Example 12 Long Stretched Film 12 T4 C1 2.0x 52 45 140 ⊚ C.Example 1 Long Stretched Film 13 T5 A1 2.0x 52 45 140 Δ C. Example 2Long Stretched Film 14 T5 B1 2.0x 52 45 140 Δ C. Example 3 LongStretched Film 15 T5 C1 2.0x 52 45 140 Δ

TABLE-2 Used Film Orientation Variation of Obtained Long Stretching UsedLong Stretch Thickness Angle In-Plane Re Widthwise Stretched Film DeviceFilm Ratio (μm) (°) (nm) Orientation Angle Example 13 Long StretchedFilm 16 T2 A1 2.0x 52 45 140 ⊚ Example 14 Long Stretched Film 17 T2 B12.0x 52 45 140 ◯ Example 15 Long Stretched Film 18 T2 C1 2.0x 52 45 140◯ Example 16 Long Stretched Film 19 T4 A1 2.0x 52 45 140 ⊚ Example 17Long Stretched Film 20 T4 B1 2.0x 52 45 140 ◯ Example 18 Long StretchedFilm 21 T4 C1 2.0x 52 45 140 ◯ C. Example 4 Long Stretched Film 22 T5 A12.0x 52 45 140 Δ C. Example 5 Long Stretched Film 23 T5 B1 2.0x 52 45140 X C. Example 6 Long Stretched Film 24 T5 C1 2.0x 52 45 140 X

TABLE-3 Used Film Orientation Variation of Obtained Long Stretching UsedLong Stretch Thickness Angle In-Plane Re Widthwise Stretched Film DeviceFilm Ratio (μm) (°) (m) Orientation Angle Example 19 Long Stretched Film25 T2 A2 2.0x 25 45 140 ⊚ Example 20 Long Stretched Film 26 T2 B2 2.0x25 45 140 ◯ Example 21 Long Stretched Film 27 T2 C2 2.0x 25 45 140 ◯Example 22 Long Stretched Film 28 T4 A2 2.0x 25 45 140 ⊚ Example 23 LongStretched Film 29 T4 B2 2.0x 25 45 140 ◯ Example 24 Long Stretched Film30 T4 C2 2.0x 25 45 140 ◯ C. Example 7 Long Stretched Film 31 T5 A2 2.0x25 45 140 Δ C. Example 8 Long Stretched Film 32 T5 B2 2.0x 25 45 140 XC. Example 9 Long Stretched Film 33 T5 C2 2.0x 25 45 140 X

TABLE 4 Obtained Image Display Obtained Circular Color Device PolarizingPlate Used Long Stretched Film Unevenness Example 25 Organic EL Display1 Circular Polarizing Plate 1 Long Stretched Film 1 ◯ Example 26 OrganicEL Display 2 Circular Polarizing Plate 2 Long Stretched Film 2 ◯ Example27 Organic EL Display 3 Circular Polarizing Plate 3 Long Stretched Film3 ◯ Example 28 Organic EL Display 4 Circular Polarizing Plate 4 LongStretched Film 4 ⊚ Example 29 Organic EL Display 5 Circular PolarizingPlate 5 Long Stretched Film 5 ⊚ Example 30 Organic EL Display 6 CircularPolarizing Plate 6 Long Stretched Film 6 ⊚ Example 31 Organic EL Display7 Circular Polarizing Plate 7 Long Stretched Film 7 ◯ Example 32 OrganicEL Display 8 Circular Polarizing Plate 8 Long Stretched Film 8 ◯ Example33 Organic EL Display 9 Circular Polarizing Plate 9 Long Stretched Film9 ◯ Example 34 Organic EL Display 10 Circular Polarizing Plate 10 LongStretched Film 10 ⊚ Example 35 Organic EL Display 11 Circular PolarizingPlate 11 Long Stretched Film 11 ⊚ Example 36 Organic EL Display 12Circular Polarizing Plate 12 Long Stretched Film 12 ⊚ C. Example 10Organic EL Display 13 Circular Polarizing Plate 13 Long Stretched Film13 Δ C. Example 11 Organic EL Display 14 Circular Polarizing Plate 14Long Stretched Film 14 Δ C. Example 12 Organic EL Display 15 CircularPolarizing Plate 15 Long Stretched Film 15 Δ

TABLE 5 Obtained Image Display Obtained Circular Color Device PolarizingPlate Used Long Stretched Film Unevenness Example 37 Organic EL Display16 Circular Polarizing Plate 16 Long Stretched Film 16 ⊚ Example 38Organic EL Display 17 Circular Polarizing Plate 17 Long Stretched Film17 ◯ Example 39 Organic EL Display 18 Circular Polarizing Plate 18 LongStretched Film 18 ◯ Example 40 Organic EL Display 19 Circular PolarizingPlate 19 Long Stretched Film 19 ⊚ Example 41 Organic EL Display 20Circular Polarizing Plate 20 Long Stretched Film 20 ◯ Example 42 OrganicEL Display 21 Circular Polarizing Plate 21 Long Stretched Film 21 ◯ C.Example 13 Organic EL Display 22 Circular Polarizing Plate 22 LongStretched Film 22 Δ C. Example 14 Organic EL Display 23 CircularPolarizing Plate 23 Long Stretched Film 23 X C. Example 15 Organic ELDisplay 24 Circular Polarizing Plate 24 Long Stretched Film 24 X Example43 Organic EL Display 25 Circular Polarizing Plate 25 Long StretchedFilm 25 ⊚ Example 44 Organic EL Display 26 Circular Polarizing Plate 26Long Stretched Film 26 ◯ Example 45 Organic EL Display 27 CircularPolarizing Plate 27 Long Stretched Film 27 ◯ Example 46 Organic ELDisplay 28 Circular Polarizing Plate 28 Long Stretched Film 28 ⊚ Example47 Organic EL Display 29 Circular Polarizing Plate 29 Long StretchedFilm 29 ◯ Example 48 Organic EL Display 30 Circular Polarizing Plate 30Long Stretched Film 30 ◯ C. Example 16 Organic EL Display 31 CircularPolarizing Plate 31 Long Stretched Film 31 Δ C. Example 17 Organic ELDisplay 32 Circular Polarizing Plate 32 Long Stretched Film 32 X C.Example 18 Organic EL Display 33 Circular Polarizing Plate 33 LongStretched Film 33 X

TABLE 6 Obtained Circular Polarizing Color Obtained Image Display DevicePlate Used Long Stretched Film Unevenness R. Example 1 Liquid CrystalDisplay Device 301 Circular Polarizing Plate 13 Long Stretched Film 13 ◯R. Example 2 Liquid Crystal Display Device 302 Circular Polarizing Plate14 Long Stretched Film 14 ◯ R. Example 3 Liquid Crystal Display Device303 Circular Polarizing Plate 15 Long Stretched Film 15 ◯ C. Example 10Organic EL Display 13 Circular Polarizing Plate 13 Long Stretched Film13 Δ C. Example 11 Organic EL Display 14 Circular Polarizing Plate 14Long Stretched Film 14 Δ C. Example 12 Organic EL Display 15 CircularPolarizing Plate 15 Long Stretched Film 15 Δ

As shown in TABLE-1, the long stretched films 1 to 12 corresponding toExamples 1 to 12 were good as compared with the long stretched films 13to 15 corresponding to Comparative Examples 1 to 3 since the variationof the orientation angle in the width direction was below ±0.6°.Particularly, the long stretched films 4, 5, 6, 10, 11 and 12 obtainedusing the stretching devices T2, T4 in which the gripping tools releasedthe long stretched film such that the straight line connecting the griprelease points was parallel to the width direction of the long stretchedfilm were good since the variation of the orientation angle in the widthdirection was below ±0.4°.

As shown in TABLE-2, the long stretched films 16 to 21 corresponding toExamples 13 to 18 were good as compared with the long stretched films 22to 24 corresponding to Comparative Examples 4 to 6 since the variationof the orientation angle in the width direction was below ±0.6°.Particularly, the long stretched films 16, 19 obtained using thenorbornene-based resin as the thermoplastic resin were good since thevariation of the orientation angle in the width direction was below±0.4°.

As shown in TABLE-3, the long stretched films 25 to 30 corresponding toExamples 19 to 24 were good as compared with the long stretched films 31to 33 corresponding to Comparative Examples 7 to 9 since the variationof the orientation angle in the width direction was below ±0.6°.Particularly, the long stretched films 25, 30 obtained using thenorbornene-based resin as the thermoplastic resin were good since thevariation of the orientation angle in the width direction was below±0.4°.

As shown in TABLE-4, the organic EL displays 1 to 12 corresponding toExamples 25 to 36 were good as compared with the organic EL displays 13to 15 corresponding to Comparative Examples 10 to 12 since there was nodifference in tinge or such a difference in tinge as not to cause anyproblem as a product. Particularly, the organic EL displays 4 to 6, 10to 12 obtained using the stretching devices T2, T4 in which the grippingtools released the long stretched film such that the straight lineconnecting the grip release points was parallel to the width directionof the long stretched film were good since there was no difference intinge.

As shown in TABLE-5, the organic EL displays 16 to 21 and 25 to 30corresponding to Examples 37 to 48 were good as compared with theorganic EL displays 22 to 24 and the organic EL displays 31 to 33corresponding to Comparative Examples 13 to 18 since there was nodifference in tinge or such a difference in tinge as not to cause anyproblem as a product. Particularly, the organic EL displays 16, 19, 25and 28 obtained using the norbornene-based resin as the thermoplasticresin were good since there was no difference in tinge.

As shown in TABLE-6, the liquid crystal display devices 301 to 303corresponding to Reference Examples 1 to 3 had little difference intinge as compared with the organic EL displays 13 to 15 corresponding toComparative Examples 10 to 12. These problems were found to be observedwhen the long stretched film was applied to the organic EL displays.

1. A method for producing a long stretched film, comprising at least astep of forming a long film made of thermoplastic resin, an obliquestretching step of delivering the long film in a specific directiondifferent from a winding direction of a long stretched film afterstretching and obliquely stretching the long film in a direction of anangle exceeding 0° and below 90° with respect to a width direction whilegripping and conveying opposite end parts of the long film by aplurality of gripping tools of an oblique stretching device and awinding step of winding the long stretched film after the obliquestretching step, wherein: the oblique stretching device includesgripping tool travel support tools at opposite sides of the travelinglong film; each of the gripping tool travel support tools at theopposite sides includes a plurality of gripping tools; the same numberof the gripping tools are provided at the opposite sides; and acombination of the gripping tools forming a gripping tool pair isconstantly the same at grip start points where the long film is grippedby the gripping tools.
 2. A method for producing a long stretched filmaccording to claim 1, wherein, in the oblique stretching step, travelroute lengths and traveling speeds at the opposite sides per lap fromthe grip start points where the long film is gripped by the plurality ofgripping tools of the gripping tool travel support tools at an entranceside of the oblique stretching device to the grip start points at theentrance side of the oblique stretching device by way of grip releasepoints where the long film is released are equal.
 3. A method forproducing a long stretched film according to claim 1, wherein, in theoblique stretching step, the traveling speeds of the gripping tools areincreased and decreased until the gripping tools grip the long filmagain after releasing the long stretched film so that the gripping toolsof the same combination are aligned at the grip start points.
 4. Amethod for producing a long stretched film according to claim 1,wherein, in the oblique stretching step, a straight line connecting thegrip release points where the gripping tools release the long stretchedfilm is parallel to the width direction of the long stretched film.
 5. Amethod for producing a long stretched film according to claim 1, whereinan in-plane retardation of the long stretched film is 120 to 160 nm. 6.A method for producing a long stretched film according to claim 1,wherein the thermoplastic resin used is norbornene-based resin.
 7. Amethod for producing a long stretched film according to claim 1, whereina film thickness of the obtained long stretched film is 10 to 35 μm.